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Electric  Locking 


By 


JAMES   ANDERSON 

Signal  Inspector,  New  York  Central  Railroad. 

Including  a  number  of  chapters  which  appeared  originally  in  the 
Railway  Signal  Engineer, 


Published  by 

SIMMONS-BOARDMAN    PUBLISHING    COMPANY 
New  York  Chicago  Cleveland  Washington 


Copyright 

Simmons-Boardman   Publishing    Company 

1918 


PREFACE 


rT~M  I  K   modern   necessity    for   speed,   for  heavier  and   longer 

^  ... 

trains,  and  the  demand  of  the  public  for  greater  facilities, 

both  freight  and  passenger,  have  increased  the  complexity  of 
railroad  operation,  resulting  in  increased  difficulties  for  signal 
engineers  in  providing  immunity  from  accidents.  For  this 
reason  the  tendency  in  modern  signaling  practice  has  been  to 
secure  increased  safety  by  decreasing  the  human  element  as  a 
vital  factor  and  substituting  the  more  dependable  automatic 
operation  of  devices — Electric  Locking.  So  little  information  is 
to  be  had  on  this  important  subject  that  it  is  hoped  many  railroad 
men  will  find  this  book  of  value. 

j.  A. 

Cleveland,  Ohio, 
November  .30,  1917. 


CONTENTS 

Preface    - 


i.    Inception  of  Electric  Locking    -  7 

Preliminary  Considerations;  Classification ; 
Evolution ;  Kinds  of  Apparatus ;  Track  In- 
strument, Relays,  Indicators,  Annunciators, 
Time  Release,  Mechanical  Time  Lock,  Lever 
Locks. 

[I.    The  Track  Circuit    -  28 

Single  and  Double  Rail ;  Normally  Open  ;  Lo- 
cation of  Relays ;  Broken  Rail  Protection ; 
Fouling  Protection  at  Crossings,  Turnouts, 
Switches,  Crossovers,  Slip  Switches,  Gaunt- 
lets. 

III.  Trap  Circuits      -  50 

IV.  Indication  Locking    -  58 

For  Mechanically  Operated  Signals ;  for  Me- 
chanically Operated  Switches  ;  Reliability  ; 
Dynamic  Indication  ;  Polarized  Switch  Indi- 
cation ;  At  Electric  Interlockings ;  G.  R.  S. 
Scheme  ;  Hall  Scheme  ;  Union,  A.  C. ;  Union, 
Bi-current;  Union,  Type  F;  Electropneu- 
matic. 

V.    Section  Locking  -  -  85 

The  Detector  Bar;  Lockings  at  Mechanical 
Plants ;  Relays  vs.  Lever  Locks ;  Electric 
Bolt-lock;  Precautions  in  Designs. 

VI.     Route  Locking  ...  -     103 

Purpose  ;  Requirements  ;  At  Grade  Crossings 
not  Interlocked ;  Crossing  Releases ;  Door 
Locks ;  Stick  Release ;  At  Junctions ;  Route 
Levers ;  Emergency  Releases ;  Combined 
Route  and  Indication  Locking;  At  Power 
Interlockings. 


VII.     Stick  Locking  -      -     124 

Requirements;  Time  Locks;  Time  Releases; 
Without  a  Stick  Relay;  With  Semi-Auto- 
matic  Signals ;  Crossing  Protection ;  At 
Power  Interlockings;  In  Manual  Block  Ter- 
ritory ;  Stick  and  Indication,  Stick  and  Sec- 
tion Locking ;  Emergency  Releases. 

VIII.    Approach  Locking  -  -     143 

Requirements  ;  Approach  Indicator  ;  Audible 
Annunciator ;  Stick  Relay  Energized  and  De- 
energized  ;  On  Single-track ;  At  Electric 
Railway  Crossings  ;  At  Power  Interlockings ; 
Combined  Approach  and  Section  Locking; 
Combined  Approach  and  Indication;  Emer- 
gency Release;  Advance  Locking;  Lever 
Locks. 

IX.    Sectional  Route  Locking      -      -      -     158 

Requirements ;  Lock  Wire ;  Scheme  A ; 
Scheme  B ;  Scheme  C ;  Scheme  D ;  Scheme 
E;  Scheme  F;  Scheme  G;  Scheme  H; 
Scheme  J. 

X.    Check  Locking    -  -      -  180 

Requirements ;  Arrangement  of  Mechanical 
Locking;  Traffic  Direction  Preference;  The 
Tower  Director;  Advance  Signal  Arrange- 
ment. 

XL    Outlying  Switch  Locking    -      -      -     187 

Mechanical  Arrangement;  Electrical  Ar- 
rangement ;  Hand  Switch  Control ;  Indica- 
tion ;  Lever  Lock  Control ;  Tower  Instru- 
ment Control;  At  Power  Plants;  Communi- 
cating Devices. 

XII.     Bridge  Locking  -  195 

Control  of  Bridge  Engine  or  Motor;  Bridge 
Locks;  Rail  Locks;  Circuit  Controllers; 
Bridge  Coupler;  Track  Circuits. 

XIII.  Testing    -  -  -    204 

XIV.  Maintenance  -    -      -      -      -      -      -    213 

Safety  Precautions ;  Emergency  Instruc- 
tions; Inspection;  Failures. 


PRELIMINARY    COXSIDERATIOXS 

Inception  of  Electric  Locking.  In  the  early  days  of  rail- 
way signaling,  when  interlockings  were  not  universally  adopted 
as  a  means  of  controlling  switches  and  signals,  the  switches  were 
thrown  by  operating  levers  mounted  near  them,  and  the  operator, 
being  close  to  the  function  operated  and,  after  having  given  his 
hand  signal  for  the  train  to  proceed,  w7as  able  to  watch  the  move- 
ment of  the  passing  train,  so  there  was  no  danger  of  his  inad- 
vertently throwing  a  switch  under  a  moving  train  or  in  the  face 
of  an  approaching  train  to  which  a  hand  signal  had  already  been 
given.  The  advantage  of  concentrating  the  switches  as  much  as 
possible,  so  that  they  could  be  worked  from  a  central  point,  soon 
became  evident,  as  they  could  thereby  be  protected  by  a  much 
smaller  number  of  signals  than  would  be  necessary  if  a  signal 
were  placed  for  every  switch.  Also  increased  traffic  and  the  conse- 
quent necessity  for  facilitating  the  handling  of  trains  at  certain 
congested  points  made  it  urgent  to  substitute  for  the  old  cum- 
bersome method  of  throwing  the  switches  a  more  convenient 
arrangement.  Thus  the  levers  for  controlling  the  switches  in  a 
given  locality  were  assembled  in  a  common  frame,  suitably  inter- 
locked and  mounted  in  a  tower  at  a  distance  from  most  of  the 
switches,  so  that  they  could  all  be  operated  from  a  central  point 
When  at  this  time  fixed  signals  were  adopted,  and  also  operated 
from  such  central  points  to  give  information  to  the  engineman. 
instead  of  the  formerly  employed  hand  signals,  it  became  necessarj 
to  devise  some  means  not  only  for  the  purpose  of  indicating  to  the 
leverman  that  the  unit  had  responded  to  a  given  lever  movement 
and  that  the  switch  or  signal  being  operated  had  fully  and  com- 
pletely performed  the  movement  intended,  but  also  make  the 
movement  of  the  trains  immune  from  dangers  caused  by  errors  on 
the  part  of  the  operator.  This  was  the  advent  of  mechanical 
interlocking  machines;  and  so  far  as  to  prevent  the  display  of 
clear  signals  being  given  simultaneously  over  conflicting  routes 
or  for  the  clearing  of  a  signal  not  yet  prepared  to  receive  a  train, 
it  proved  very  satisfactory.  Notwithstanding  this  vast  improve- 
ment experience  soon  taught  that  the  errors  committed  on  the 
part  of  the  leverman  through  carelessness,  rapid  manipulation  of 
the  levers,  negligence  or  hasty  action,  were  numerous. 

7 


ELECTRIC   LOCKING 

In  order  to  make  the  movement  of  trains  through  an  interlock- 
ing plant  perfectly  safe  it  has  been  deemed  necessary  to  impose 
certain  restrictions  upon  the  leverman  and  partly  relieve  him  of 
the  responsibilities  incidental  to  the  safe  handling  of  trains 
approaching  and  passing  through  an  interlocking  plant ;  in  other 
words,  means  which  would  not  only  insure  the  operators  being 
more  deliberate  in  their  actions,  but  also  make  them  respect  rules 
which,  under  ordinary  working  conditions,  would  be  disregarded 
and  eventually  result  in  disaster.  To  accomplish  this,  various 
means  have  been  devised — some  purely  mechanical,  others  elec- 
tro-mechanical. For  the  control  of  the  latter  devices,  numerous 
different  circuit  schemes  have  been  developed  to  suit  existing  con- 
ditions. The  means  adopted  are  all  automatically  controlled,  1/ 
which  again  follows  the  tendency  of  modern  signaling  practice 
in  securing  increased  safety  by  decreasing  the  human  element  as 
a  vital  factor  and  substituting  the  more  dependable  automatic 
control  of  devices. 

Classification  of  Electric  Locking.  The  various  schemes 
for  the  supplementary  protection  of  an  interlocking  plant  (partly 
exclusive  of  the  mechanical  locking  in  the  interlocking  machine 
and  often  in  conjunction  with  it)  can  be  classed  under  one  gen- 
eral head  of  ELECTRIC  LOCKING. 

The  Railway  Signal  Association  manual  defines  electric  lock- 
ing as  being  "The  combination  of  one  or  more  electric  locks  and 
controlling  circuits  by  means  of  which  levers  of  an  interlocking 
machine,  or  switches  or  other  devices  operated  in  connection  with 
signaling  and  interlocking,  are  secured  against  operation  under 
certain  conditions." 

It  may  be  classified  as  follows :  Indication  locking,  section  lock- 
ing, route  locking,  stick  locking,  approach  locking  and  sectional 
route  locking.  These  classes  are  what  may  be  termed  essentials 
of  electric  locking.  Additional  special  locking  features  are  fre- 
quently desired  or  required  by  the  peculiarities  of  local  conditions 
or  arrangements  of  the  interlocking  facilities.  The  most  import- 
ant of  these  auxiliary  electric  locking  features  are  check  locking, 
bridge  locking  and  outlying  switch  locking,  each  providing  the 
particular  protection  that  their  nomenclatures  imply. 

Evolution  of  Electric  Locking.     Without  attempting  to  go 

8 


PRELIMINARY    CONSIDERATIONS 

into  the  history  of  electric  locking,  a  few  words  will  be  said  with 
regard  to  the  development  of  these  different  classes  of  electric 
locking. 

\n  an  interlocking  machine  the  levers  are  so  interconnected 
that  a  route  must  be  set  up  properly  before  a  signal  can  be  cleared 
and  after  it  is  cleared  the  route  cannot  be  changed  unless  the  sig- 
nal is  again  restored  to  the  stop  position.  But  with  ordinary 
interlocking  it  is  possible  after  having  restored  the  signal  normal 
to  change  a  switch  ahead  of  a  train  or  throw  it  under  a  train  and 
afterwards  clear  a  conflicting  signal.  This  led  to  the  introduc- 
tion of  the  detector  bar,  for  switch  protection,  but,  as  it  was  con- 
sidered an  unsatisfactory  protective  medium  by  many  signal  men 
(see  Chapter  IV),  it  was  partially  superseded,  particularly  at 
large  plants,  by  electric  switch  locking,  which  prevented  a  switch 
from  being  thrown  under  a  train  by  the  train  shunting  the  track 
circuit  and  locking  the  lever  so  it  could  not  be  moved.  This  was 
the  advent  of  the  track  circuit  and  the  "Section  Locking."  After- 
wards this  locking  was  extended  to  fouling  points  on  the  track 
and  also  to  take  care  of  switches  in  advance  of  the  switch  over 
which  the  train  was  moving. 

With  this  protection  on  all  switches,  if  a  leverman  put  his  sig- 
nal normal  the  switches  were  still  locked  up  until  the  train  had 
passed  over  them.  This  constituted  what  is  termed  ''Route  Lock- 
ing." At  busy  terminals  this  protection  proved  satisfactory  from 
a  safety  standpoint,  but  from  an  operating  point  of  view,  it  did 
not  admit  of  expeditious  handling  of  traffic.  Hence  the  electric 
switch  locking  was  arranged  to  release,  as  soon  as  a  train  had 
passed,  a  switch  and  permit  the  locking  to  take  effect  in  which- 
ever direction  the  train  was  running.  "Sectional  Route  Locking" 
is  the  term  applied  to  this  class  of  electric  locking. 

Although  precautions  in  locking  and  handling  of  trains  were 
observed,  as  just  stated,  practice  soon  proved  that  where  high 
speed  of  trains  was  indulged  in  no  dependence  could  safely  be 
placed  on  the  leverman,  and  it  was  found  to  be  necessary  to  adopt 
means  to  prevent  a  leverman  from  careless  or  premeditated 
changes  of  route  once  given  and  accepted  by  an  engineman.  Thus 
the  locking  was  so  arranged  that  when  a  train  entered  a  track 
circuit,  3,000  ft.  or  4,000  ft.  from  the  distant  signal,  or  as  soon 
as  a  distant  or  home  signal  was  cleared,  it  locked  the  levers  so 
that  the  signal  could  be  placed  normal,  but  the  route  could  not  be 

9 


ELECTRIC   LOCKING 

changed  until  the  train  had  passed  the  home  signal.     This  was 
termed  "Approach  Locking"  or  ''Stick  Locking." 

With  the  advent  of  power-operated  signals  and  power  inter- 
lockings,  it  became  necessary  to  add  another  safety  feature, 
namely,  "Indication  Locking,"  which  would  insure  the  corre- 
spondence of  the  position  of  the  function  and  the  lever.  Where 
tracks  uniting  two  interlocking  plants  cease  to  be  adequate  for 
the  needs  of  traffic  between  them  when  the  use  of  each  track  is 
restricted  to  train  movements  in  one  direction  only,  "check  lock- 
ing" is  employed.  This  provides  electric  locking  between  towers 
by  the  signals  in  one  interlocking  being  inter-controlled  with 
those  of  another  when  the  signals  govern  opposing  train  move- 
ments over  tracks  common  to  both.  Where  a  switch  is  located 
close  to  an  interlocking,  but  too  far  away  from  the  tower  to  be 
operated  from  the  interlocking  machine,  protection  is  provided 
by  electrically  locking  the  switch  so  that  it  cannot  be  moved  with- 
out the  knowledge  and  consent  of  the  leverman.  This  is  called 
"outlying  switch  locking."  A  drawbridge  or  other  type  of  oper- 
ating bridge  is  generally  provided  with  locking  so  that  the  bridge 
is  locked  in  its  closed  position  and  so  interlocked  with  the  signals 
approaching  the  bridge  that  they  cannot  be  cleared  unless  the 
bridge  is  in  the  proper  position  and,  consequently,  constitute 
"bridge  locking." 

Locking  Circuit  Design.  Electric  locking  circuits  admit  of 
innumerable  variations  and  nearly  every  installation  requires 
some  special  schemes  of  inter-connections  and  new  designs,  which 
often  radically  differ  from  the  standard  practice  of  the  particular 
road  for  which  the  protection  is  contemplated.  There  are,  how- 
ever, certain  generic  features  adhered  to,  which  obtain  in  most 
cases  and  which  form  a  basis  for  the  more  complicated  circuits 
designed  to  meet  complex  situations.  It  is  their  differentiation 
which  often  produces  the  seeming  complexity,  when  a  circuit  is 
viewed  as  a  whole.  It  is  therefore  the  intention  to  present  first 
each  style  of  locking  in  its  basic  form  and  also  the  more  simple 
application  of  the  different  styles  of  electric  locking  as  classified 
by  the  Railway  Signal  Association,  then  present  their  modifica- 
tions and  finally  the  various  styles  combined,  to  suit  more  com- 
plex situations.  It  will  be  found,  that  very  seldom  is  only  one 
style  of  electric  locking  applied  to  a  plant,  as  in  most  cases  a 

10 


PRELIMINARY    CONSIDERATIONS 

combination  of  different  styles  is   Found  best  adapted  to  needs. 

Many  differences  exist  in  the  art  and  practice  of  signaling  of 
railroads  and  there  are  naturally  minor  points  of  superiority  in 
the  methods  of  safeguarding  trains  in  all  systems.  A  designer 
of  electric  locking  circuits  should  therefore  not  only  give  careful 
attention  to  the  minutest  details  of  the  circuit  itself,  but  should 
also  obtain  intimate  knowledge  of  the  workings  of  the  signal 
appliances  involved  in  order  to  properly  know  how  a  dangerous 
condition  is  most  liable  to  occur,  and  thereby  add  features  in  the 
lucking  circuit  which  will  guard  against  them.  While  provisions 
must  be  made  for  the  normal  condition  of  affairs,  the  dangers 
incident  to  exceptional  circumstances  must  be  met  by  exceptional 
precautions.  The  possible  dangerous  conditions  that  seldom  hap- 
pen are  the  ones  that  prove  most  fatal  when  they  do  occur,  and 
no  interlocking  plant  can  be  considered  perfectly  safe  except  with 
all  such  contingencies  anticipated  and  all  probable  dangers 
averted.  For  instance,  the  failures  at  danger  for  a  signal  indica- 
tion can  only  wrongly  delay  a  train  and  cause  an  unnecessary 
stop  ;  but  failures  at  clear,  by  giving  the  engineer  a  proceed  indi- 
cation when  such  may  not  be  safe,  are  the  only  ones  that  can 
really  be  called  dangerous.  It  should  be  remembered,  however, 
that  the  saving  of  an  unnecessary  stop  also  means  a  saving  of 
money,  and  while,  as  just  stated,  a  clear  signal  failure  is  the  only 
dangerous  derangement  of  a  signal  system,  the  danger  failure 
should  also  receive  due  consideration  when  making  provisions 
for  safeguarding  train  movements.  The  governing  principle  in 
electric  locking,  as  well  as  in  all  other  branches  of  signaling, 
should  be: —  a  failure  of  any  part  of  the  apparatus  or  circuits 
should  always  lie  on  the  side  of  safety. 

What  Class  to  Apply.  While  it  is  evident  that  electric  lock- 
ing is  necessary  to  employ  as  an  adjunct  to  interlockings,  the 
question  of  what  type  to  apply  to  interlockings  of  various  type- 
ami  sizes  is  generally  one  of  individual  opinion  of  the  signaling 
officials  for  the  road  where  the  protection  is  to  be  applied  and, 
to  some  degree,  will  also  depend  upon  the  complexity  of  the  track 
layout,  the  traffic  facilities  desired,  the  economical  aspects  and 
the  protection  required.  The  usual  practice,  of  course,  has  been 
to  increase  the  amount  of  protection  applied  in  proportion  to  the 
size  and  the  importance  of  the  interlocking  plant.     Thus,  at  large 

11 


ELECTRIC   LOCKING 

and  congested  yards,  terminals  and  busy  grade  crossings,  the 
most  elaborate  arrangements  of  electric  locking  protection  are 
usually  installed.  Smaller  plants  are  generally  provided  with 
electric  locking  protection  of  a  less  complicated  nature,  and  often 
with  quite  primitive  apparatus,  which  appears  crude  when  com- 
pared with  modern  appliances.  This,  of  course,  seems  very  log- 
ical, although  the  wisdom  of  so  doing,  when  considered  from 
various  viewpoints,  is  sometimes  questionable.  For  instance,  at 
busy  plants  the  levermen  have  no  time  for  anything  else  but 
attending  to  the  manipulation  of  levers,  and  by  constant  practice 
they  become  extremely  proficient,  and  experience  has  proven  that 
mistakes  are  rarely  made.  An  error  once  committed  on  the  part 
of  the  leverman,  however,  might  prove  a  serious  matter,  and  the 
expense  therefore  of  auxiliary  apparatus  and  intricate  circuits, 
providing  all  protection  possible,  is  justified.  On  the  other  hand, 
a  leverman  at  a  small,  isolated  interlocking  plant  on  a  branch  line 
of  light  traffic,  has  an  excessive  amount  of  time  on  his  hands 
between  trains.  Being  far  removed  from  any  supervising  author- 
ity and  the  plant  probably  not  being  as  perfectly  maintained,  nor 
as  repeatedly  inspected  as  the  main  line  plants,  he  is  left  most  of 
the  time  to  his  own  resources.  As  it  is  human  nature  to  experi- 
ment with  machinery,  so  it  is  perfectly  natural  for  these  men  to 
try  all  kinds  of  experiments  with  the  signaling  appliances,  prob- 
ably to  discover  flaws  or  in  some  way  to  beat  the  combination. 
At  night  there  are  also  usually  few  trains  and  nothing  to  keep 
the  leverman's  mind  off  sleep.  If  he  should  happen  to  go  to 
sleep  and  a  train  suddenly  shows  up  there  is  a  great  possibility  of 
his  so  manipulating  the  levers  as  to  cause  a  derailment.  It  would 
therefore  seem  just  as  important  to  equip  these  plants  with  most 
auxiliary  safety  devices  commonly  found  at  the  more  important 
plants,  provided,  of  course,  that  the  management  finds  such  addi- 
tional expenditures  warranted. 

Apparatus  Used  in  Electric  Locking.  In  connection  with 
electric  locking  there  are  various  kinds  of  accessory  apparatus 
which  are  referred  to  throughout  the  chapters  to  follow,  and 
which  may  need  some  description  as  to  their  function,  control  and 
operation  when  applied  in  connection  with  electric  locking. 

Track  Instrument.     A  track  instrument   is    used    in    places 

12 


PRELIM IX AR ) '    COX  SI  VERA  TIOXS 

where  conditions  will  not  permit  the  use  of  a  track  circuit,  and  it 
will  either  effect  the  locking"  or  the  release  of  the  locking  of  a 
plant.  It  is  adopted  for  use  by  roads  not  employing  track  circuits, 
or  at  isolated  places  where  the  maintenance  of  a  track  circuit 
would  be  prohibitory,  or  at  electric  railroads  using  the  rails  as  a 
return  for  the  propulsion  current. 

Interlocking  Relay.  An  interlocking  relay  is  used  on  single 
track  roads  where  the  current  of  the  traffic  is  in  both  directions 
and  where  a  certain  operation  is  desired  to  take  effect  only  with 
the  train  running  in  one  direction.  It  is  also  used  on  double 
track  roads  at  crossings  where  the  density  of  traffic  requires  some 
means  whereby  a  release  of  the  route  locking  may  be  accom- 
plished as  soon  as  a  train  has  passed  over  the  crossing,  but  is  still 
within  the  limits  of  the  interlocking.  There  are,  broadly  speak- 
ing, two  types  of  interlocking  relays,  and  under  ordinary  condi- 
tions either  type  will  answer  the  purpose  for  which  it  is  designed 
There  are  circuit  arrangements,  however,  which  necessitate  the 
use  of  a  type  of  an  interlocking  relay  which,  in  addition  to  its 
regular  interlocking  features,  also  contains  certain  distinct  fea- 
tures not  embodied  in  the  other  types.  This  feature,  which  is  the 
employment  of  the  interlocking  parts  as  a  part  of  the  circuit  con- 
trolled by  the  relay,  while  it  may  not  be  recommended  as  a  good 
design  on  account  of  lightning  trouble,  etc.,  is  in  many  cases  an 
essential  requirement. 

Fig.  1  shows  diagrammatically  an  example  of  the  method  by 
which  the  interlocking  features  are  accomplished  in  a  relay  when 
the  interlocking  parts  are  not  used  as  a  part  of  the  circuit  to  be 
controlled.  "A,"  "B,"  "C"  and  "D"  show,  respectively,  the  posi- 
tion of  the  armatures  and  interlocking  parts  with  the  train  located 
on  different  parts  of  the  track  circuit.  It  will  be  noted  that  there 
is  no  electrical  connection  between  the  interlocking  arms  or  the 
contact  arms,  so  that  a  circuit  can  only  be  completed  between 
points  1  and  2  and  between  3  and  4. 

Fig.  2  shows  in  diagrammatic  form  the  operation  of  an  inter- 
locking relay  that  has  the  interlocking  parts  utilized  for  the  con- 
trol circuit.  As  the  contact  arms  are  also  used  for  interlocking 
purposes,  with  the  relay  in  a  position  as  shown  in  diagram  "D," 
a  circuit  will  be  completed  from  1  to  2  through  the  contact  arms. 
This  is  the  feature  which  makes  it  possible  to  arrange  a  circuit 

13 


ELECTRIC   LOCKING 

so  that  a  train  entering  one  track  section  on  one  side  of  a  grade 
crossing  will  effect  the  locking  of  a  route  and  the  train  entering 
the  section  section  will  effect  the  release  of  the  locking. 

While  the  R.  S.  A.  has  adopted  a  standard  symbol  for  inter- 


HHtka.h    Z 


% 


ftg^ 


-f*i#- 


15 


7 


% 


5     <o 


8 


2 


I 


id 


FIG.   1. 


% 


I  train  y|~ 


FIG.   2. 


5.  ± 

,  T 


=0,'   I   e0=  * 


^t£TT 


±A       C^ 


1: 


FIG.    3. 


14 


FIG.    4. 


PRELIMINARY    CON  SID  ERA  TIONS 

locking  relays,  this  symbol  cannot  represent  both  types  of  the 
relays  just  described.  Thus  Fig.  3  should  be  used  as  the  symbol 
for  the  last  described  type  of  an  interlocking  relay. 

Stick  Relays.  A  stick  relay  is  used  when  it  is  desired  to  pre- 
vent certain  operations  to  take  place  until  other  operations  or 
conditions  are  fulfilled.  It  is  employed  to  a  great  extent  in  elec- 
tric locking,  sometimes  as  a  track  relay,  but  more  often  as  a  line 
relay.  It  may  be  said  to  be  one  of  the  most  employed  mediums 
in  electric  locking  and  can  be  used  to  advantage  in  any  of  the 
different  styles. 

It  is  a  relay  whose  controlling  circuit  is  so  arranged  that  one 
of  its  own  front  contacts  closes  a  path  for-  the  current  through 
its  own  coils.  A  stick  relay  may  be  so  connected  into  a  circuit  that 
its  normal  position  may  be  either  energized  or  de-energized.  A 
normally  open  stick  relay  scheme  is  shown  in  Fig.  4.  "C"  and 
"D"  represent  push  buttons,  but  may  in  practical  use  be  substi- 
tuted with  either  relay  contacts,  slow  release  contacts,  floor  push 
contacts,  signal  circuit  controllers,  lever  contacts,  contacts  on  a 
track  instrument  or  a  pair  of  car  wheels  and  axle.  It  will  be 
noted  that  with  the  closing  of  the  contact  "D"  the  stick  relay 
"R"  will  become  energized  through  contact  "C,"  wire  "G"  and 
its  own  coils.  An  immediate  break  of  contact  "D"  will  not  affect 
the  position  of  the  relay,  which  will  remain  energized,  being  held 
through  contact  "C,"  wire  "H,"  its  own  coils  and  its  own  front 
point  "E."  The  breaking  of  contact  "C,"  however,  will  imme- 
diately release  the  stick  circuit  and  cause  the  relay  to  drop.  In 
order  to  again  pick  up  the  relay,  the  same  operation  must  take 
place,  that  is,  contacts  "C"  and  "D"  must  be  made,  while  the  re- 
lease of  the  armature  is  caused  by  the  breaking  of  contact  "C" 
only.  Thus  a  stick  relay  circuit  will  always  have  some  controlling 
contacts  which,  in  the  present  case,  is  switch  "C."  The  energi- 
zation of  the  relay  depends  entirely  upon  this  contact.  A  stick 
relay  circuit  has  also  a  pick  up  contact  "D"  and  a  pick  up  wire 
"G" ;  "H"  is  generally  called  the  stick  up  wire  and  "E"  the  stick 
point.  Contacts  "F"  are  to  be  used  for  circuits  controlled  by  the 
stick  relay.  The  circuits  for  a  normally  energized  stick  relay  will 
be  the  same,  excepting  that  the  successive  steps  in  the  operation 
will  be  the  reverse  of  the  normally  de-energized  scheme. 

The  question  of  the  employment  of  the  normally  de-energized 

15 


ELECTRIC    LOCKING 

or  normally  energized  stick  relay  often  puzzles  a  novice  in  circuit 
work,  and  it  may  be  stated  here  that  the  control  of  anything  elec- 
trically by  an  open  circuit  is  unreliable  for  many  reasons  well 
understood  by  up-to-date  circuit  men.  In  using  an  open  circuit 
the  electric  current  is  only  called  into  action  when  the  work  must 
be  done,  with  no  assurance  that  it  will  perform  the  work  or  pro- 
duce the  desired  result. 

Tower  Indicators.  In  connection  with  most  classes  of  elec- 
tric locking  it  is  desirable  that  means  be  provided  to  convey 
information  to  the  leverman  with  regard  to  the  operation  of  sig- 
naling apparatus  or  the  approach  of  trains.  Tower  indicators  are 
the  general  term  applied  to  such  indication  devices  that  are  de- 
signed for  use  in  interlocking  towers.  The  necessity  for  employ- 
ing auxiliary  devices  of  this  type  is  often  due  to  local  conditions 
such  as  the  presence  of  buildings,  trees  and  bridges,  or  curves 
and  grades  in  the  track.  Adverse  weather  conditions  also  often 
prevent  the  leverman  from  properly  observing  the  movement  of 
trains.  Due  to  the  location  of  a  signal,  it  is  often  impossible  for 
the  leverman  to  note  its  operation  and  at  night,  where  back  lights 
on  signals  are  not  provided,  no  check  is  had  upon  the  operation 
of  the  apparatus  without  the  employment  of  indicators.  An  indi- 
cator employed  to  show  the  presence  of  a  train  on  a  certain  length 
of  track  is  termed  a  track  indicator  or  track  repeater.  An  indi- 
cator employed  to  signify  the  approach  of  a  train  to  the  inter- 
locking is  called  an  approach  indicator ;  and  one  that  indicates 
the  position  of  a  signal,  a  signal  repeater. 

Indicators  arranged  as  signal  repeaters  generally  have  a 
movable  miniature  semaphore  arm  which  is  shaped  and  assumes 
a  position  similar  to  that  of  the  signal  by  which  it  is  controlled. 
An  indicator  of  this  type  is  designed  to  give  indication  in  two  or 
three  positions. 

Indicators  arranged  for  approach  indication  are  generally  of 
the  disk  type  and  known  as  the  disappearing  disk  type  of  an  indi- 
cator. Track  indicators  should  be  of  a  distinctly  different  type 
than  the  others.  A  type  like  the  revolving  disk  or  one  whose 
movable  and  visible  parts  are  designed  in  the  form  of  a  dumb-bell 
is  recommended. 

Where  it  is  necessary  to  distinguish  between  two  or  more  indi- 
cators, a  designating  number  or  letter  is  painted  either  on  the 

16 


PRELJM1X.  IKY    CONSIDERATIONS 

outer  face  plate  or  the  front  of  the  cover.  The  former  method 
may  be  considered  preferable,  since  the  covers  of  instruments 
mounted  side  by  side  might  accidentally  become  interchanged, 
["lie  designation  given  an  indicator  might  be  the  number  of  the 
signal  with  a  prefix  designating  the  type  or  the  track  section  to 
which  the  instrument  is  connected,  or  any  other  method  of  desig- 
nation adopted. 

Tower  indicators  are  generally  arranged  with  contact  fingers 
to  be  used  for  the  control  of  circuits.  Many  railroads  object  to 
the  employment  of  these  contacts  for  circuits,  as  they  consider  the 
operation  and  adjustments  obtainable  with  tower  indicators,  due 
to  the  many  movable  parts,  too  unreliable  for  the  actuation  of 
important  circuits.  The  indicators,  therefore,  merely  act  as  re- 
peaters for  relays,  the  relays  being  used  for  the  make  and  break 
of  electrical  contacts. 

Illuminated  Track  Indicators.  The  use  of  separate  indi- 
cators to  repeat  the  condition  of  the  various  track  circuit  sec- 
tions has  in  many  up-to-date  installations  given  way  to  illumi- 
nated track  diagrams,  which  undoubtedly  give  to  the  leverman 
better  information  as  to  the  movement  of  trains  over  the  inter- 
locking than  that  given  by  separate  indicators.  Illuminated  track- 
indicators  have  the  track  layout  painted  on  ground  glass  and 
show  whether  or  not  a  track  section  is  occupied,  by  electric  lamps 
placed  behind  the  glass,  the  lamps  being  controlled  by  the  track 
circuit.  These  types  of  indicators  are  usually  more  expensive  to 
maintain  than  other  types  on  account  of  the  comparatively  large 
amount  of  current  constantly  used.  Where  the  track  arrange- 
ment is  very  complex  and  a  large  number  of  track  circuits  neces- 
sary, separate  indicators  of  the  semaphore  or  a  similar  type,  one 
for  each  track  circuit,  is  somewhat  confusing,  as  it  is  necessary 
for  the  leverman  to  always  keep  in  mind  to  which  circuit  each 
one  is  connected.  With  illuminated  track  indicators  the  neces- 
sary information  about  each  track  section  is  given,  even  when 
trains  are  not  visible  to  the  leverman.  In  addition,  all  functions 
are  numbered  on  the  diagram,  thus  making  it  serve  two  purposes 
and  eliminating  the  necessity  for  a  separate  track  diagram. 

Another  effective  visual  indication  is  to  install  a  light  at  each 
switch  lever  in  the  interlocking  machine  and  so  arrange  the  con- 
trol through  the  route    or    other    electric    locking  relays  that  a 

17 


ELECTRIC   LOCKING 

visual  indication  is  obtained  showing  whether  or  not  the  lever 
may  be  manipulated.  Often  both  illuminated  track  diagrams  and 
lever  lights  are  installed  at  one  plant,  thereby  giving  the  leverman 
two  visual  indications  as  to  the  occupancy  of  tracks.  This 
method  of  conveying  information  to  the  leverman  is  particularly 
desirable  where  sectional  route  locking  is  employed,  as  the  move- 
ment of  a  train  and  the  consequent  release  of  the  electric  locking 
can  be  watched  during  any  train  movement  over  the  plant.  In 
place  of  signal  repeaters  lever  lights  are  often  used  and  the  con- 
trol so  arranged  that  the  lights  will  burn  when  the  signal  is  clear. 

Annunciators.  In  addition  to  the  visual  indication  provided 
by  approach  indicators,  annunciators  are  employed,  to  give  an 
audible  indication  that  a  train  has  passed  a  certain  point  when 
approaching  an  interlocking  plant.  These  will  call  the  lever- 
man's  attention  to  the  condition  they  indicate  when  he  is  other- 
wise occupied.  They  are  not  only  necessary  at  congested  points, 
but  also  at  places  where  the  distance  of  an  approaching  train  from 
the  interlocking  cannot  be  gauged  with  a  sufficient  degree  of 
accuracy  to  avoid  delays  either  to  the  approaching  train  or  to 
other  trains  whose  movements  are  dependent  upon  it.  Electric 
bells  or  buzzers  are  usually  employed  as  audible  annunciators. 

It  is  often  desirable,  particularly  where  no  visual  indicators 
are  employed,  to  use  bells  or  buzzers  having  different  tones  for 
different  tracks  in  order  to  avoid  confusion  if  more  than  one  train 
should  approach  an  interlocking  simultaneously.  Bells  with  dif- 
ferent forms  of  gongs,  giving  a  variety  of  tones,  are  known  as 
the  dome,  tea,  cow  and  sleigh  bell  types.  Single  stroke  and 
vibrating  types  of  bells  are  also  often  employed  as  two  distinc- 
tive types. 

Screw  Releases.  This  is  the  general  term  for  manually 
operated  instruments  which  require  a  given  length  of  time  to 
complete  their  movement,  the  operation  being  performed  by  tha 
leverman.  These  instruments  are  known  by  numerous  different 
names,  as  slow  releases,  time  releases,  electric  hand  time  releases, 
electro  mechanical  hand  time  releases,  and  mechanical  hand  time 
releases.  They  are  all  functioned  to  accomplish  the  same  thing, 
and  that  is  to  release  the  electric  locking  in  an  interlocking  ma- 
chine which,  because  beinsf  out  of  order  or  for  some  other  abnor- 

18 


PRELIMINARY    COX  SI  DURA  TIONS 

mal  condition  such  as  an  error  on  the  part  of  the  leverman,  holds 
locked  a  lever  which  it  is  desirable  to  move  in  order  to  avoid 
delaying'  a  train.  To  prevent  hasty  action  by  a  disturbed  or  ex- 
cited leverman  the  releases  are  so  constructed  that  they  can  be 
operated  only  by  turning  a  screw  a  certain  predetermined  number 
of  times.  The  release  must  always  be  returned  to  its  original 
position  before  the  plant  is  again  restored  to  normal  operating 
conditions  and  to  the  control  of  the  leverman.  This  is  necessary, 
for  when  the  electric  locking  is  released  by  the  leverman  in  an 
emergency,  conditions  must  be  made  such  that  the  interlocking 
plant  cannot  be  used  until  the  releasing  device  has  been  placed 
normal,  otherwise  there  would  be  nothing  to  prevent  the  operator 
from  maintaining  the  release  in  the  reverse  position  and  thus 
keeping  the  electric  locking  ineffective. 

The  screw  release  has  two  positions:  the  normal  position 
which  it  occupies  when  nothing  is  operated,  and  the  reverse  posi- 
tion which  it  occupies  during  its  movement.  In  the  electric  screw 
releases  the  turning  of  the  handle  and  the  consequent  movement 
of  the  operating  parts  will  break  contacts  controlling  electric 
circuits,  and  when  the  release  is  fully  reversed  will  make  con- 
tacts for  other  circuits.  In  electro-mechanical  screzv  releases  the 
turning  of  the  handle  not  only  causes  the  make  and  break  of 
contacts  controlling  electric  circuits,  but  in  addition  thereto,  being 
located  on  the  locking  bed  of  the  interlocking  machine,  it  will 
lock  one  or  more  levers  in  a  certain  position  until  it  is  again  put 
normal.  A  mechanical  screw  release  effects  the  release  of  a  lock 
by  mechanical  means  only,  in  that  the  reversal  of  the  screw  re- 
lease raises  one  lock  armature  by  a  lifting  dog  operated  bv  the 
release,  while  at  the  same  time  certain  levers  in  the  interlocking 
machine  are  locked  by  dogs  attached  to  the  bar  operated  by  the 
screw  release,  in  this  way  insuring  that  the  release  is  placed 
normal  before  other  routes  can  be  set  up. 

The  time  required  to  operate  the  screw  release  generally  varies 
in  length  from  ten  seconds  to  ten  minutes,  the  adjustment  in  the 
length  of  time  depending  upon  local  conditions.  The  time  inter- 
val element  in  a  screw  release  should  receive  careful  consideration 
and  the  length  of  time  required  in  the  release  of  the  locking  for 
one  plant  may  not  be  suitable  for  another.  If  the  traffic  at  a 
plant  is  very  heavy,  the  time  limit  would  necessarily  have  to  be 
short  so  that  no  long  delays  in  train  movements  will  be  experi- 

19 


ELECTRIC   LOCKING 

enced,  and  if  traffic  is  light  the  time  limit  may  he  made  as  long 
as  two  or  three  minutes.  Another  item  enters  into  the  time  in- 
terval element,  and  that  is  the  minimum  breaking  distance  of  the 
trains  at  the  plant.  If  an  engineman  consumes  as  long  as  three 
minutes  between  the  distant  and  the  home  signals  it  is  evident 
that  he  can  stop  in  this  distance  in  three  minutes  should  the  dis- 
tant and  the  home  be  put  to  stop  against  him.  In  other  words, 
the  time  should  be  so  adjusted  that  it  will  not  be  possible  for  the 
operator  to  put  a  distant  or  home  signal  to  stop  that  has  already 
been  accepted  by  the  engineman,  then  operate  his  screw  release, 
thereby  releasing  the  route  and  next  open  a  derail  in  the  face  of 
the  train.  Thus  the  time  required  to  operate  the  screw  release 
should  be  long  enough  to  permit  a  train  to  come  to  a  stop  after 
a  signal  has  been  taken  away  from  it,  before  it  is  possible  for 
the  operator  to  change  the  route. 

Screw  releases  may  be  substituted  with  hand  switches  or  knife 
switches,  but  these  must  be  placed  downstairs  in  the  tower  or  at 
a  distance  from  the  operator,  so  that  it  will  take  him  some  time 
to  reach  it  in  order  to  give  the  requisite  time  (as  with  a  screw 
release)  before  one  route  is  released  and  another  set  up.  This 
type  of  a  release  was  very  common  in  the  early  days  of  signaling, 
and  when  used  in  present  practice  generally  is  placed  in  a  box 
with  glass  front. 

Emergency  Switch.  In  addition  to  the  screw  release,  which 
in  most  cases  is  employed  only  to  release  the  route  locking  while 
still  maintaining  the  other  parts  of  the  protection  combined  with 
the  route  locking,  an  emergency  switch  is  often  introduced  to 
take  care  of  any  failures  either  in  the  track  circuit,  stick  relay 
circuit  or  local  battery  troubles.  The  emergency  switch  is  gen- 
erally enclosed  in  a  locked  case  with  glass  cover  and  placed  down- 
stairs in  the  tower.  Thus,  in  the  event  of  trouble,  the  towerman 
is  compelled  -to  go  downstairs,  break  the  glass  of  the  box  and 
throw  the  switch,  after  which  he  will  operate  his  screw  release  or 
other  releasing  device.  As  in  the  case  of  screw  releases,  the  cir- 
cuit through  the  emergency  switch  is  arranged  so  that  it  must 
be  placed  normal  before  the  plant  is  restored  to  normal  operating 
condition.  A  snap  switch  is  often  employed  as  an  emergency 
switch.  With  this  a  quick  motion  is  possible  when  placed  from 
one  position  to  another  by  the  operation  of  a  spring. 

20 


PRELIMINARY   CONSIDERATIONS 

Time  Release.  A  time  release  is  frequently  employed  for 
the  release  of  an  electric  lock  or  other  circuits  used  in  connection 
with  the  lock  circuit  when  a  time  interval  is  required  for  the  re- 
lease ;  but  where  it  is  undesirable  to  have  the  operator  manipulate 
the  instrument  during  the  entire  time  interval.  This  gives  the 
operator  an  opportunity  to  perform  his  other  duties  while  the 
release  is  doing  its  own  manipulating  after  having  been  started 
in  its  action  by  the  operator. 

There  are  several  different  kinds  of  time  releases,  including 
the  mercury,  clock  work,  electric  and  thermostatic,  all  operated 
as  indicated  by  their  names.  They  will  make  or  break  a  circuit 
any  predetermined  number  of  seconds  or  minutes  after  it  has 
been  put  in  action.  It  may  be  put  in  action  either  automatically, 
when  it  is  attached  to  a  lever,  where  the  placing  of  the  lever  in 
a  certain  position  will  cause  its  operation ;  or  manually,  when  the 
operator  by  the  turning  of  a  knob  or  the  closing  of  a  circuit  puts 
it  in  action.  The  maximum  time  interval  which  can  be  secured 
with  a  time  release  is  ten  minutes.  Automatic  recording  devices 
as  counters  are  often  installed  on  releases  and  the  records  care- 
fully checked  to  insure  strict  adherence  to  prescribed  rules  and  as 
a  check  upon  the  errors  committed  by  various  levermen. 

Other  Release  Schemes.  On  some  railroads  the  release  of 
the  electric  locking  for  emergency  purposes  is  accomplished  by 
sealing  the  lock  itself  with  a  car  seal  or  similar  device  instead  of 
the  use  of  a  time  release.  Then  if  there  is  a  real  need  of  releas- 
ing the  locking  the  leverman  can  break  the  seal,  open  and  pick 
the  lever  lock  and  manipulate  the  lever.  When  this  is  done  the 
leverman  and  maintainer  are  jointly  held  responsible  for  any- 
thing that  may  happen.  The  seals,  sealing  iron,  etc.,  must  only 
be  in  the  possession  of  a  responsible  person  and  not  the  leverman. 
This  scheme  is  not  to  be  recommended  because  of  the  likelihood 
of  a  simple  mistake  on  the  part  of  the  leverman  making  necessary 
the  exposure  of  the  lock  to  further  manipulation  of  levers  with- 
out any  restriction  or  check  until  again  sealed  up. 

Mechanical  Time  Lock.  A  mechanical  time  lock  is  em- 
ployed in  connection  with  the  locking  in  an  interlocking  machine 
and  is  used  in  lieu  of  electric  locking  circuit.  It  will  introduce 
a  time  element  between  the  placing  of  the  signal  or  other  lever 

21 


ELECTRIC   LOCKING 

normal  and  prevent  any  change  in  the  route  governed  by  the  sig- 
nal upon  whose  lever  it  is  placed  until  released  by  the  mechanical 
time  lock. 

Floor  Pushes.  A  floor  push  is  used  when  a  momentary  elec- 
tric contact  is  desired  to  pick  up  an  electric  lock,  a  stick  relay 
or  any  other  electric  device.  They  are  particularly  adapted  for 
the  control  of  lever  locks  not  having  circuit  controllers  attached 
to  them.  They  are  fixed  in  the  flocr  where  the  signalman  can 
conveniently  close  the  circuit  by  pressing  downward  on  a  button 
with  his  foot.  A  push  button,  hand  switch  or  table  button  is  fre- 
quently used  in  place  of  a  floor  push.  The  employment  of  the 
floor  push,  however,  is  more  advantageous,  as  it  leaves  the  opera- 
tor free  to  use  his  hands  for  other  work,  as,  for  instance,  the 
manipulation  of  a  lever  in  the  interlocking  machine.  A  knife 
switch  cannot  be  used  as  a  substitute  for  a  floor  push  because  the 
operator  is  liable  to  leave  the  switch  in  the  closed  position  and 
permanently  maintain  a  closed  circuit  through  the  lock  coils, 
which  the  switch  was  installed  to  prevent. 

Lever  Locks.  An  electric  lever  lock  is  a  device  which  locks 
the  levers  of  an  interlocking  machine  to  prevent  its  movement 
until  it  is  released  by  an  electro-magnet.  It  consists  of  either  a 
solenoid  with  a  movable  core  or  plunger,  or  a  vertical  or  hori- 
zontal magnet  with  an  armature.  The  locking  parts  consist  of  a 
sliding  bar  or  a  locking  segment  that  moves  in  unison  with  the 
lever  to  which  it  is  attached.  An  electric  lock  may  be  placed  on 
a  switch,  derail,  facing  point  lock,  movable  point  frog,  signal, 
route,  master,  check  lock,  bridge  lock,  rail  lock  or  an  outlying 
switch  lock  lever.  It  may  lock  any  of  these  levers  in  either  one 
of  various  positions,  or  two  of  them  in  combination.  An  electric 
lock  arranged  to  hold  a  lever  locked  in  its  full  normal  position 
is  termed  a  normal  lock;  one  holding  it  locked  in  the  full  reverse 
position  a  reverse  lock ;  one  holding  it  locked  in  the  full  normal 
and  full  reverse  position  a  normal  and  reverse  lock ;  one  holding 
the  lever  locked  in  the  understroke  position,  so  that  it  is  possible 
to  reverse  the  lever,  but  not  possible  to  place  it  full  normal,  is 
called  a  half  reverse  lock ;  one  holding  the  lever  locked  in  the 
understroke  position,  so  that  it  is  possible  to  place  a  lever  full 
normal,  but  not  possible  to  fully  reverse  it,  is  called  a  half  normal 

22 


FREIJU1X.  IRY    COXSIDERATIOX  S 

lock ;  and  one  which  permits  the  lever  to  be  moved  between  the 
normal  and  reverse  indication  or  latching  positions,  but  not  fully 
normal  nor  fully  reversed,  is  called  an  indication  lock.  A  combi- 
nation of  the  full  normal  and  half  reverse  lock  is  frequently  used. 
Where  a  lever  is  to  be  locked  in  two  positions  the  notches  cut 
must,  of  course,  be  far  enough  apart  so  as  to  have  sufficient  metal 
between  them  for  the  necessary  mechanical  strength.  There  are 
cases  where  it  is  necessary  to  employ  two  locks  on  account  of  this 
consideration,  each  lock  employed  for  the  locking  of  the  lever 
in  one  position.     Fig.  5  shows  the  symbols  for  the  various  tvpes 

ti.      ti      h      ti 

A  B  C  0 

ti     ti     h     h 

¥     H     ? 


H 


FIG.   S. 


of  electric  locks.  "A"  is  a  normal  lock,  "B"  a  reverse  lock,  "C" 
a  normal  and  reverse  lock,  "D"  a  half  reverse  lock,  "E"  a  half 
normal  lock,  "F"  an  indication  lock  and  "G"  a  normal  and  half 
reverse  lock.  Where  a  lock  is  arranged  to  lock  a  lever  in  one 
position  only  it  is  possible  to  make  arrangements  so  that  the  drop- 
ping of  the  lock  armature  with  each  operation  of  the  lever  is 
assured.  For  example,  in  Fig.  5-H,  which  shows  a  half  reverse 
lever  lock,  a  detector  1  is  attached  to  insure  that  the  lock  arma- 
ture is  not  permanently  picked  up  due  to  residual  magnetism. 
Should  it  happen  to  stick  up,  the  lever  cannot  be  reversed  owing 
to  the  lock  extension  striking  the  detector  1.  This  type  of  a  seg- 
ment is  very  desirable  to  use  whenever  possible,  as  it  acts  as  a 
check  with  each  manipulation  of  a  lever. 

On  interlocking  machines  having  what  is  called  lever  locking, 
the  lever  lock  is  arranged  to  lock  the  lever  in  either  its  full  nor- 

23 


ELECTRIC    LOCKING 

mal  or  reverse  positions.  Interlocking  machines  having  what  is 
termed  latch  locking  must  have  the  electric  lock  arranged  to 
engage  with  the  locking  in  its  operating  connection  in  such  a 
manner  that  the  locking  is  held  in  a  position  which  prevents  the 
latch  from  being  moved.  A  lever  lock  magnet  with  the  lever  in 
the  extreme  normal  and  reverse  positions  should  always  be  de- 
energized  by  so  arranging  the  control  circuit  that  only  during  its 
actual  use  (that  is,  while  the  lever  is  being  manipulated)  must 
current  flow  through  it.  The  reason  for  this  is  partly  to  effect  a 
saving  in  current  consumption,  but  principally  to  protect  the  lock 
magnet  from  residual  magnetism,  which  will  have  a  tendency  to 
retain  the  lock  armature  in  a  picked  up  position.  Hence,  where 
a  normal  or  reverse  lever  lock  on  a  mechanical  interlocking  ma- 
chine is  controlled  by  contacts  operated  by  the  lever  upon  which 
it  is  placed,  the  notch  in  the  lock  segment  is  so  cut  as  to  permit 
a  slight  preliminary  movement  of  the  latch  or  lever,  enough  to 
close  the  lever  lock  circuit.  Such  close  adjustments,  however,  are 
often  difficult  to  maintain,  as  experience  has  taught  that  with  a 
slight  amount  of  lost  motion  in  the  many  parts  between  the  latch 
handle  and  the  lever  lock,  it  has  happened  that  the  latch  shoe  has 
gotten  to  the  top  of  the  rocker  before  the  lever  lock  has  taken 
effect.  Many  railroads,  therefore,  employ  a  floor  push  for  normal 
and  reverse  locks  on  a  mechanical  interlocking  machine. 

Cross  Protection.  Cross  protection  is  one  of  the  vital  fac- 
tors to  be  considered  in  circuit  designing  and  one  which  enters 
conspicuously  as  a  safety  factor  when  arranging  circuits  for  indi- 
cation or  electric  locking  purposes.  Cross  protection  is  provided 
to  take  care  of  "crosses,"  and  "crosses''  in  signaling  are  the  acci- 
dental contact  of  conducting  wires,  causing  either  an  increased 
current  in  a  wire  or  reversing  its  polarity  or  energizing  a  wire 
which  should  be  dead,  and  thereby  producing  a  derangement  of 
apparatus.  The  employment  of  low  voltage  apparatus,  which  is 
the  practice  in  electric  locking,  makes  extra  precautions  necessary 
to  prevent  improper  movements  of  the  apparatus  as  a  result  of 
crosses  on  account  of  their  being  sensitive  to  outside  influences. 

A  few  rules  will,  better  than  any  description,  give  a  correct  con- 
ception of  the  necessary  precautions  to  be  taken  with  the  design 
of  locking  circuits  to  insure  that  the  circuits  provide  adequate 
cross-protection  for  the  apparatus  rontrolled. 

24 


PRELIMINARY    CONSIDERATIONS 

Rule  i  : — Controlling'  circuits  should  always  be  so  arranged 
that  a  cross  will  cause  a  signal  to  indicate  stop,  a  switch  to  remain 
in  the  position  which  corresponds  with  the  position  of  the  lever, 
an  electric  locking  device  to  maintain  its  locked  position  and  to 
remain  so  until  the  fault  is  corrected. 

When  considering  the  cross  protection  of  devices  used  for  elec- 
tric locking  purposes  by  the  shunting  method  an  arrangement,  as 
required  in  Rule  1,  is  possible  but  not  practicable,  and  if  installed 
mav  lead  to  complications  and  serious  trouble  that  would  prove 
far  worse  than  the  derangements  which  the  shunts  were  designed 
to  prevent. 

Rule  2\ — All  connections  or  contacts  depended  upon  for  cross 
protection  must  also  be  used  in  operation,  so  that  any  failure  or 
break  which  would  impair  their  usefulness  as  a  cross  protection 
medium  would  also  prevent  the  operation  of  the  signal  or  switch, 
thus  acting  as  a  constant  automatic  check  without  the  use  of  any 
extra  contrivances  for  this  purpose. 

As  Rule  2  covers  the  safest  method  of  applying  the  shunt  cross- 
protection  recommended  in  Rule  1,  it  will,  of  course,  not  be 
applicable  to  electric  locking  circuits. 

Rule  S  '■ — A  device  receiving  energy  should  have  all  controlling- 
contacts  located  between  it  and  the  source  of  energy,  thus  having 
one  side  of  the  device  connected,  (a)  directly  to  common  so  that 
no  controlling  contact  will  be  shunted  out  in  the  case  of  a  ground, 
or  (b)  directly  to  battery  so  that  the  controlling  contacts  will  be 
shunted  out  in  the  case  of  a  ground.  The  application  of  require- 
ments  (a)  and  (b)  in  Rule  3  depends  largely  upon  whether  the 
circuit  considered  is  to  be  an  open  circuit  or  a  closed  circuit 
proposition,  and  whether  the  release  of  a  locking  circuit  or  the 
safe  operation  of  a  locking  device  is  depending  upon  the  pick  up 
of  a  relay  or  the  dropping  of  a  relay.  An  example  of  the  arrange- 
ment of  a  circuit  meeting  the  requirements  (a)  in  Rule  3  is  shown 
in  Fig.  6.  The  relay  or  device  (c)  is  normally  energized  and  all 
controlling  contacts — being  relay,  switch  box,  signal  or  lever 
contacts — are  located  between  the  relay  and  battery  positive, 
while  battery  negative  is  connected  directly  at  the  coil.  It  will 
be  noted  that  a  cross  between  wires  1  and  2  as  at  "X"  will  shunt 
out  relay  C  and  cause  its  de-energization,  which  in  the  present 
case  will  be  on  the  side  of  safety.  A  ground  to  common  at  "Y" 
will  also  shunt  the  relay  out. 

25 


ELECTRIC    LOCKING 


Had  the  circuit  been  arranged  as  shown  in  Fig".  7,  where  posi- 
tive battery  is  connected  directly  at  the  coil,  a  cross  at  "X"  would 
cause  the  relay  to  stay  picked  up,  thereby  not  only  creating  a 
dangerous  condition,  but  also  preventing  its  discovery  until  pos- 
sibly a  wreck  or  derailment  would  call  the  operator's  attention  to 
the  derangement.  A  ground  at  "Y"  would  also  cause  the  energi- 
zation of  the  relay.  Fig.  8  represents  an  open  circuit  proposition, 
and  here  the  safety  of  the  circuits  controlled  through  the  relay 
depends  upon  its  de-energized  state.  Thus,  a  cross  at  "X"  be- 
tween wires  1  and  2  will  cause  the  energization  of  the  relay  by 
the  shunting  out  of  the  controlling  contacts,  and  a  ground  at  "Y" 
will  also  pick  up  the  relay.      A    couple    of    simple    circuits  will 


Of 


^ 


C\ 


■\  f-°" 


UrX 


*— 


ur 


W 


FIG.   6. 


FIG.   9. 


FIG.    7. 


FIG.   10. 


FIG.   8. 


clearly  demonstrate  the  application  of  either  requirement :  stick 
relay  circuits  will  be  shown  as  examples.  Fig.  9  shows  a  normally 
energized  (normally  closed)  stick  relay  circuit  which,  for  simpli- 
city's sake,  is  arranged  as  controlled  by  track  instruments.  Track 
instrument  "A"  is  the  starting  or  locking  instrument,  while  "B" 
is  the  releasing  or,  in  this  case,  the  pick-up  instrument.  "A"  is 
a  normally  closed  and  "B"  a  normally  open  track  instrument. 
This  being  a  closed  circuit  arrangement,  the  devices  to  be  con- 
trolled will  naturally  be  broken  through  the  front  points  of  the 
stick  relay  "D,"  which  again  means  that  the  release  or  the  normal 
condition  of  the  electric  locking  is  depending  upon  the  energized 
state  of  relay  "D,"  and  its  de-energized  position  should  indicate 
a  danger  condition.  It  will  be  noted  that  the  breaking  of  the 
contact  on  instrument  "A"  will  drop  the  stick  relay,  which  will 
not  pick  up  again  until  contact  on  instrument  "B"  is  closed.  A 
cross  between  the  control  wires  as  at  "W"  will  cause  the  drop- 
ping of  the  relay,  and  grounds  at  "X,"  "Y,"  "Z"  or  any  place  in 
the  circuit  will  have  the  same  effect.  The  opposite  of  what  has 
been  said  in  regard  to  Fig.  9  is  true  in  regard  to  Fig.  10.     Here 

26 


PRELIMINARY   CONSIDERATIONS 

the  relay  is  normally  de-energized  and  any  cross  or  ground 
should  cause  its  energization,  as  the  circuits  to  be  controlled  by 
it  are  broken  through  back  points.  In  this  circuit  the  closing  ot 
track  instrument  "B"  will  energize  the  relay,  and  the  breaking  of 
"A"  will  again  cause  its  de-energization.  A  cross  between  the 
control  wires  at  "X"  will  energize  relay,  and  the  same  will  be 
effected  by  a  ground  at  "X.'  A  ground  at  "Z"  and  "Y"  after  the 
relay  has  been  picked  i]p  will  keep  it  in  an  energized  state. 

There  are  exceptional  cases  where  the  connecting  of  positive 
battery  to  a  normally  de-energized  relay  should  not  be  arranged, 
that  is,  in  places  where  the  energization  of  the  normally  de-ener- 
gized stick  relay  will  release  the  electric  locking.  In  such  cases, 
of  course,  negative  battery  should  be  connected  directly  at  the 
relay  coils. 

It  will  be  well  to  bear  in  mind  when  considering  cross  protec- 
tion in  circuit  designing  that  the  possibility  of  a  ground  or  a  wire 
taking  common  through  some  faulty  insulation  is  greater  than 
the  chance  of  positive  battery  current  being  introduced  into  same 
through  a  cross. 

The  observation  of  the  rules  just  set  forth  is  most  essential  for 
a  successful  result  in  all  cases  where  apparatus  is  to  be  safe- 
guarded against  crosses. 


27 


II 

THE  TRACK  CIRCUIT 

Introductory.  Almost  every  style  of  electric  locking  ar- 
rangement requires  a  track  circuit  as  a  lock  or  release  medium 
and,  while  the  purpose  of  electric  locking  is  to  safeguard  an  inter- 
locking plant  from  negligence  on  the  part  of  the  operator,  it  is 
of  vital  importance,  in  designing  such  protection,  that  the  track 
circuit  is  given  due  consideration.  Without  a  proper  co-operation 
in  the  workings  of  the  track  circuit  and  the  locking  features,  the 
protection  cannot  be  considered  complete.  While  one  style  of 
electric  locking  may  suit  a  certain  condition,  it  must  be  under- 
stood that  there  is  the  choice  of-  a  number  of  different  styles  or 
arrangements  of  track  circuits  which  might  be  employed  in  con- 
nection with  it.  The  more  elementary  principles  and  applications 
of  a  track  circuit  are  too  well  known  to  need  any  description.  In 
the  present  article,  therefore,  there  will  be  treated  only  the 
arrangement  of  track  circuits  at  interlocking  plants  so  far  as  it 
affects  the  electric  locking  of  such  plants,  and  also  the  most  ad- 
vantageous methods  of  insulating  in  order  to  derive  the  most 
complete  protection  possible  for  existing  conditions  from  an  elec- 
tric locking  point  of  view.  Broadly  speaking,  track  circuits  may 
be  divided  into  two  distinct  classes,  viz..  the  normally  closed  and 
the  normally  open  track  circir"  Each  class  may  again  be  sub- 
divided into  single  rail  and  double  rail  circuits. 

The  Normally  Closed  Track  Circuit.  Of  these  the  nor- 
mally closed  track  circuit  is  the  one  principally  in  use,  being  the 
most  dependable,  particularly  in  places  where  the  track  circuit  is 
employed  for  the  semi-automatic  control  of  the  signals  in  addition 
to  the  electric  locking.  The  normally  closed  track  circuit  derives 
its  name  from  the  manner  in  which  the  track  relay  is  energized, 
as  the  track  section  being  unoccupied  and  the  rails  unimpaired, 
the  battery  will  keep  the  track  relay  energized  by  a  constant  flow 
of  current.  Thus,  a  circuit  maintained  on  the  closed  circuit  prin- 
ciple will  very  effectively  give  warning  of  many  dangerous  condi- 
tions in  a  signal  system.  It  will,  by  causing  the  de-energization 
of  the  track  relay,  give  warning  of  the  presence  of  a  train,  a  car 
detached  from  a  train,  broken  rail,  and  by  proper  arrangement 
of  insulated  joint  will  detect  a  car  inside  the  clearance  of  fouling 

28 


THE    TRACK    CIRCUIT 

point  at  siding's,  or  an  open  switch  where  an  outlying  switch  is 
located  within  the  limits  of  an  interlocked  home  signal. 

The  Normally  Open  Track  Circuit.  The  normally  open 
track  circuit  is  used  to  a  very  limited  extent  and  principally  only 
in  places  where  non-automatic  signals  are  in  use  and  where  the 
track  circuit  is  employed  for  no  other  purpose  but  the  electric 
locking.  Contrary  to  the  closed  track  circuit,  in  the  open  circuit 
scheme  the  presence  of  a  train  will  cause  the  energization  of  the 
relay.  The  principal  reason  for  the  very  limited  employment  of 
the  normally  open  track  circuit  is  because  there  is  no  certainty  of 
the  relay  picking  up.  Any  failures  of  the  apparatus,  such  as  a 
broken  rail,  exhaustion  or  breakage  of  the  batter}'  cell  or  the 
breakage  of  any  of  the  wires  will,  of  course,  render  the  apparatus 
inoperative;  besides,  such  failures  are  not  readily  detected,  as 
they  merely  maintain  the  apparatus  in  its  normal  condition.  With 
the  normally  closed  circuit  the  reverse  is  true,  as  here  any  failure 
will  be  almost  immediately  detected  and  also  be  on  the  side  of 
safety. 

Single  and  Double  Rail  Circuits.  Single  rail  and  double 
rail  circuits  can  be  employed  in  normally  closed  and  normally 
open  track  circuits.  The  term  "single  rail  circuits"  is  derived 
from  the  fact  that  only  one  rail  in  each  part  of  the  circuit  is  insu- 
lated. The  employment  of  a  track  circuit  of  this  kind  is  made 
principally  to  avoid  the  expense  of  additional  insulated  joints, 
insulated  front  and  head  rods,  tie  plate  insulations  and  in  some 
places  pipe  line  insulations,  or  where  one  rail  is  needed  for  other 
circuits.  A  single  rail  track  circuit,  however,  is  more  liable  to 
failure  than  one  having  the  two  rails  insulated,  for  a  number  of 
obvious  reasons  the  details  of  which  it  would  be  beyond  the  scope 
of  this  article  to  enter  into.  The  common  rail  is  the  term  gener- 
ally applied  to  the  rail  in  which  there  are  no  insulated  joints; 
one  reason  for  this  being  that  it  is  often  used  as  a  common  for 
additional  circuit.  In  the  following  circuits  this  rail  is,  for  the 
sake  of  distinction,  shown  in  heavy  lines. 

Normally  Open  Circuits.  A  single  rail  application  of  a 
normally  open  track  circuit  is  shown  in  Fig.  11.  The  insulated 
joints,  while  often  placed  at  the  signal,  are  here  placed  inside  of 

29 


ELECTRIC   LOCKING 

the  derails,  thereby  avoiding  the  expense  of  insulated  switch  rods 
for  the  operation  of  the  derails.  It  is  a  common  practice,  at 
plants  for  single  track  crossings  having  a  track  circuit  which  ex- 
tends only  between  the  home  signals  for  the  operation  of  the  elec- 
tric locking,  to  arrange  the  insulated  joints  at  the  derails  in  this 
manner,  as  the  space  between  the  signal  and  the  derail  point  is 


xt  tv 

FIG.  11  A.  FIG.   11. 

generally  protected  by  the  detector  bar  "D,"  and  thus  the  require- 
ments for  the  electric  locking  protection  of  the  plant  are  fulfilled. 
The  track  circuit  is  transposed  at  the  crossing  by  connecting  a 
jumper  as  shown. 

Transpositions.  The  transposition  of  a  track  circuit  is 
effected  by  the  placing  of  insulated  joints  and  jumpers  at  some 
place  within  a  track  section  in  such  a  manner  that  the  polarity 
of  the  adjacent  rails  in  the  same  track  section  is  reversed.  The 
reasons  for  transposing  a  D.C.  track  circuit  are  manifold.  A 
high  potential  difference  between  the  rails,  effected  by  foreign  or 
stray  current  from  electric  roads  operated  in  a  close  vicinity  to 
the  track,  may  be  one  reason  for  inserting  a  transposition  in  a 
track  circuit,  in  this  way  providing  a  low  resistance  path  for  the 
stray  currents  across  the  rails  through  the  jumpers,  thereby  di- 
verting the  stray  current  from  the  track  relay.  This  will  be  more 
clear  to  the  reader  with  a  double  transposition  as  shown  in  Fig. 
11a.  Stray  currents  flowing,  as  shown  by  arrows  "X"  and  "Y," 
will  flow  through  jumpers  and  back  toward  their  respective 
sources  (arrow  "Z")  without  interfering  with  the  track  circuit 
operation.  Another  reason  for  the  necessity  of  transposition  is 
to  limit  the  dead  section  in  a  track  circuit  where  two  roads  cross 
each  other  at  an  oblique  or  acute  angle,  or  where  a  switch  in  a 
section  is  so  located  that  a  proper  insulating  warrants  it. 

"Dead"  Track  Sections.  Fig.  12  shows  a  single  rail  appli- 
cation of  a  normally  open  track  circuit  with  a  switch  in  the  block. 

30 


THE    TRACK    CIRCUIT 

The  expense  of  additional  insulated  joints  and  insulated  switch 
rods  is  here  avoided  by  the  use  of  two  insulated  joints  and  a 
jumper  and  by  the  transposition  of  the  track  circuit.  By  this 
transposition  arrangement  the  "dead"  section  is  limited  to  about 
20  feet  or  less,  so  that  no  car  or  engine  can  stand  in  this  section 
without  affecting  the  working"  of  the  relay.     In  this  connection  it 


FIG.   12. 


might  be  well  to  call  attention  to  the  fact  that  a  track  circuit,  in 
order  to  afford  full  protection  and  fulfill  the  requirements  made 
of  it,  must  be  so  designed  and  constructed  that  each  rail  of  a 
certain  length  of  track  carries  a  current  of  opposite  polarity,  as 
the  part  of  a  track  where  the  rails  happen  to  be  of  the  same 
polarity  is  cut  out  or  constitutes  what  is  generally  termed  a  "dead 
section."  A  dead  section  in  a  track  circuit  is  frequently  inevit- 
able, but  the  object  should  be  to  make  this  section  as  short  as 
possible  so  as  to  prevent  a  car  standing  across  the  rails  in  the 
dead  section  without  causing  the  track  relay  to  indicate  its  pres- 
ence. Hence,  in  a  case  like  the  present,  the  insulated  joints  "C" 
and  "D"  should  of  course  be  placed  as  nearly  opposite  as  possible 
in  order  to  reduce  to  a  minimum  the  dead  section.     In  single 


:^2b 


Mr 


IF 


FIG.   13. 


FIG.   14. 


FIG.   IS. 


FIGC   17. 


rail  circuits  it  should  always  be  observed  that  the  rail  insulated 
will  be  the  one  to  whom  battery  positive  is  connected,  as  an 
arrangement  to  the  contrary  will  facilitate  the  grounding  of  bat- 
tery positive  and,  while  not  necessarily  causing  the  false  energi- 
zation of  the  relay,  certainly  will  cause  a  constant  drain  on  the 
battery.     Fig.  13  shows  the  application  of  a  single  rail  open  cir- 

31 


ELECTRIC    LOCKING 

cuit  at  an  oblique  crossing  where  track  circuit  protection  is  pro- 
vided for  both  roads.  It  is  to  be  noted  that  the  joints  at  the 
crossing  are  arranged  so  as  to  transpose  the  circuit  with  a  view 
to  limiting  the  dead  section  and  at  the  same  time  providing  a 
common  rail.  It  is,  furthermore,  to  be  noted  that  a  train  entering 
the  track  circuit  from  any  direction  will  cause  the  energization  of 
the  relay. 

Normally  Closed  Circuits.  The  most  simple  and  at  the 
same  time  very  efficient  normally  closed  track  circuit  is  illustrated 
in  Fig.  14.  This  is  a  single  rail  circuit  and  it  will  be  observed 
that  the  relay  "B"  is  normally  energized  by  battery  "A"  through 
a  series  of  jumpers  connecting  each  of  the  positive  rails  of  the 
crossing.  The  relay  could  be  energized  by  the  placing  of  the 
track  battery  and  the  relay  in  series  with  connection  to  only  one 
positive  and  negative  rail,  but  by  employing  the  jumpers  as  a  con- 
nection between  the  battery  and  the  relay  a  constant  automatic 
check  is  obtained  which  will  detect  the  breaking  of  any  one  or 
all  of  the  jumpers,  such  an  occurrence  causing  the  de-energization 
of  the  relay.  Fig.  15  shows  the  scheme  used  in  connection  with 
a  right  angle  crossing.  The  similarity  of  this  scheme  to  that 
shown  in  Fig.  14  will  be  apparent. 

It  should  be  obvious,  however,  that  a  circuit,  where  the  battery 
used  for  the  energization  of  the  relay  is  connected  close  to  or  at 
the  relay,  cannot  be  perfectly  safe,  because  a  break  of  any  rail 
will  prevent  a  train  from  shunting  the  relay.  An  inspection  of 
Fig.  14  will  show  that  a  break  of  a  rail  at  "C"  would  prevent  a 
train  entering  that  part  of  the  track  circuit  from  shunting  .the 
relay  until  the  train  had  passed  the  rail  break. 

Location  of  Relays.  There  are  places  where  it  is  considered 
necessary  to  have  the  electric  locking  of  a  plant  take  effect  upon 
a  train  passing  the  home  signal  from  either  direction  and  not  re- 
leased until  the  train  has  passed  the  crossing.  In  such  cases  four 
separate  track  circuits  will  necessarily  be  employed,  and  a  circuit 
of  this  kind  using  single  rail  circuit  is  shown  in  Fig.  16.  It  is  a 
well-known  fact  that  in  order  to  expedite  the  release  of  the  arma- 
ture of  a  track  relay  the  relay  should  be  located  at  the  home 
signal  and  that  the  battery  ought  to  feed  the  relay  against  the 
current  of  traffic.    This,  of  course,  is  not  possible  on  single  track 

32 


THE    TRACK    CIRCUll 


roads  where  high  speed  trains  run  in  either  direction.  On  double 
track  roads  this  rule  should  be  strictly  observed,  although  at  in- 
terlocking plants  the  track  sections  as  a  rule  are  short,  and  it  is 
immaterial  at  which  point  of  the  track  section  the  relay  is  located. 
Hence,  it  has  become  the  general  practice  in  cases  where  it  is 
necessary,  to  have  the  track  circuit  terminate  at  the  crossing,  to 
locate  the  relays  there,  as  they  may  thereby  be  placed  in  the  inter- 
locking tower  and  thus  effect  the  saving  of  a  considerable  quan- 
tity of  wire,  all  the  wiring  being  confined  to  the  tower. 

In  connection  with  the  circuit  (Fig.  16)  it  will  perhaps  be  well 


FIG.   16. 


to  call  attention  to  one  error  which  may  easily  be  committed 
when  designing  or  installing  a  circuit  of  this  or  a  similar  kind 
where  one  common  connection  is  possible  from  one  side  of  the 
relays  to  the  common  rail.  It  will  be  noted  that  the  common  side 
of  the  relays  are  joined  with  jumpers  and  one  wire  connecting 
the  relays  with  the  common  rail.  This  should  be  avoided  for  the 
reason  that,  should,  for  instance,  a  break  occur  in  the  frog  rail  at 
"X,"  it  would  not  only  remain  unobserved,  but  a  train  in  section 
"E"  would  keep  track  relays  "C"  and  "II"  energized  in  series 
through  the  circuit,  as  indicated  by  arrows.  Another  style  of  a 
circuit  for  a  grade  crossing  which  may  be  used  to  advantage  is 
shown  in  Fig.  17.  Here  an  interlocking  relay  serves  the  purpose 
of  locking,  and  the  circuit  used  in  connection  with  this  arrange- 
ment may  be  designed  so  that  both  coils  of  the  relay  must  be 
energized  in  order  to  release  the  locking,  and  this  can  only  occur 
after  the  train  has  completely  passed  out  of  both  track  sections. 
The  circuit  can  also  be  arranged  so  that  a  train  passing  out  of 
one  track  circuit  into  the  other  will  release  the  electric  locking 
of  the  crossing.  In  this  latter  case  an  interlocking  relay  of  the 
style  shown  at  "C"  will  have  to  be  employed,  as  described  in 
Chapter  I.     To  further  prove  the  necessity  of  employing  a  com- 

33 


ELECTRIC    LOCKING 

mon  rail  at  acute  angle  grade  crossings,  both  rails  have  been 
shown  insulated  in  this  figure.  The  dead  section  affected  by  this 
arrangement  is  indicated  by  distance  "A,"  that  is  the  distance 
between  the  two  extreme  joints.  By  using  a  common  rail  and 
only  two  insulated  joints  the  dead  section  is  reduced  to  distance 
"B." 

Fouling  Protection.  The  fouling  point  is  that  point  on  con- 
verging tracks  where  a  car  running  toward  some  other  point  will 
come  in  contact  with  a  car  or  train  standing  or  moving  on  the 
other  track.  Thus,  by  providing  fouling  protection  for  a  certain 
piece  of  track  it  will  prevent  a  car  from  standing  on  a  turnout 
or  near  a  crossing  so  close  that  it  would  endanger  a  train  passing 
on  the  main  track.  This  is  usually  accomplished  by  extending 
the  track  circuit  to  a  point  on  a  side  track  where  there  is  suffi- 
cient clearance  between  the  two  tracks.  At  interlocking  plants  a 
derail  and  detector  bar  is  usually  placed  at  such  points,  and  no 
train  can  proceed  beyond  this  except  with  the  sanction  of  the 
operator,  this  sanction  being  expressed  by  the  clearing  of  the  sig- 
nal situated  near  the  derail,  the  lever  locking  between  the  derail 
and  the  signal  providing  against  the  clearing  of  the  signal  until 
the  derail  has  been  properly  closed.  The  detector  bar  will  pre- 
vent the  derail  from  being  thrown  to  its  normal  position  should 
a  car  happen  to  be  standing  upon  it,  and  this  in  turn,  by  the  aid 
of  the  mechanical  locking  in  the  interlocking  machine,  would 
prevent  the  clearing  of  a  signal  on  the  main  track  until  the  re- 
lease of  the  detector  bar  had  proven  that  a  movement  of  a  train 
on  the  main  track  would  be  secure  against  collisions  or  side- 
swiping.  On  well-protected  plants,  however,  this  protection  is 
not  considered  sufficient,  for  the  reason  that  the  fouling  point  on 
a  turnout  may  extend  from  200  ft.  to  400  ft.  away  from  the  main 
track,  and  several  cars  may  be  standing  between  the  derail  and 
the  turnout  starting  point  without  interfering  with  the  working 
of  the  detector  bar.  Thus,  the  employment  of  fouling  circuits  at 
interlocking  plants  is  considered  very  necessary  in  connection 
with  the  derails  provided  for  the  fouling  protection  of  main 
tracks. 

Broken  Rail  Protection.     It  should  be  recalled  that  the  ten- 
dency of  a  broken  rail  or  the  presence  of  a  car  to  de-energize  the 

34 


THE    TRACK    CIRCUIT 

track  relay  will  be  practically  the  same  if  the  occurrence  takes 
place  anywhere  in  the  track  circuit  between  the  point  where  the 
battery  leads  and  the  relay  leads  are  attached  to  them.  Hence, 
it  should  be  apparent  that  in  order  to  provide  all  protection  pos- 
sible the  leads  should  be  connected  to  the  rails  at  the  extreme  ends 
of  the  circuit,  keeping  as  much  rail  as  possible  in  series  with  the 
battery  and  the  relay.  A  true  appreciation  of  these  facts  should 
greatly  assist  the  reader  in  obtaining  a  correct  conception  of  the 
advantages  derived  from  the  different  schemes  for  effective  foul- 
ing protection  to  suit  various  conditions. 

Classification  of  Fouling  Protection.  There  are  three 
distinct  ways  to  secure  fouling  protection,  and  these  are: 

1.  By  the  so-called  multiple  or  shunt  fouling  in  which  the 
fouling  protection  is  secured  by  simply  arranging  the  insulated 
joints  so  that  the  rails  of  the  turnout  will  consist  of  one  rail  of 
each  polarity ;  in  other  words,  constitute  a  shunt  to  the  main 
circuit. 

2.  By  the  series  fouling  in  which  the  fouling  circuit  is  so 
arranged  that  one  or  both  rails  of  the  turnout  are  connected  in 
series  with  the  track  battery  for  the  main  track  circuit,  and  the 
rails  thus  used  in  the  control  of  the  track  relay  in  the  main  circuit. 

3.  By  the  employment  of  a  separate  circuit,  either  operated 
independentlv  of  the  main  track  circuit  by  the  use  of  an  extra 
relay  and  track  battery,  or  operated  in  conjunction  with  the  main 
track  circuit  by  using  its  track  battery  and  a  separate  relay. 

Of  the  three  schemes  the  shunt  fouling  is  the  one  most  com- 
monly used  at  interlocking  plants,  although  for  several  reasons 
it  is  conceded  to  be  inferior  to  the  others  with  respect  to  the  pro- 
tection afforded. 

Shunt  Fouling.  The  reasons  for  its  extensive  use  can  be 
accounted  for  when  considering  the  close  attention  and  inspection 
bestowed  upon  apparatus  and  track  connections  at  an  interlock- 
ing plant.  It  is  much  more  simple  than  any  of  the  others,  re- 
quires less  insulated  joints,  and  the  quantity  of  wire  necessary 
for  jumpers  is  reduced  to  a  minimum.  The  matter  of  reducing 
the  number  of  insulated  joints  does  not  merely  represent  the  item 
of  cutting  down  the  initial  cost  of  a  certain  plant,  but  the  future 
maintenance  must  also  be  considered,  and  the  up-keep  of  an  in- 

35 


ELECTRIC   LOCKING 

creased  number  of  joints  at  a  large  plant  will  in  time  add  con- 
siderably to  the  operating  expenses. 

Series  Fouling.  The  series  fouling  is  used  only  to  a  limited 
extent  at  interlocking  plants,  due  to  the  increased  number  of  in- 
sulated joints  and  jumpers  required,  and  also  on  account  of  the 
necessity  of  the  placing  of  extra  insulated  joints  in  the  main  line 
rail.  It  gives  more  protection  than  the  shunt  fouling.  However, 
when  summing  up  the  situation  as  to  whether  to  employ  shunt 
or  series  circuit  at  a  certain  location,  it  is  merely  a  question  of 
track  conditions,  and  if  the  advantages  present  from  a  protection 
standpoint  outnumber  the  disadvantages  existing  when  seen  from 
an  operation  point  of  view. 

Separate  Fouling  Circuit.  The  third  scheme  of  employing 
a  separate  circuit  is  decidedly  the  one  most  preferable,  but  it  re- 
quires additional  track  relays,  introducing  increased  maintenance 
expense,  so  its  use  is  mostly  restricted  to  places  where  the  fouling 
circuit  is  of  a  prohibitive  length,  which  would  either  make  a  series 
fouling  too  complex  or  expensive  or  a  shunt  fouling  too  unsafe 
or  unreliable. 


Fouling  at  Grade  Crossings.  A  grade  crossing  showing  the 
application  of  a  shunt  fouling  with  the  employment  of  a  single  rail 
track  circuit  is  illustrated  in  Fig.   18 


A  train  moving  towards 


FIG.   18. 

the  crossing  from  either  direction  on  the  fouling  track  will,  as 
soon  as  the  first  pair  of  wheels  have  passed  either  the  insulated 
joint  "C"  or  "D,"  shunt  the  track  relay  "B."  The  most  serious 
objection  offered  to  the  shunt  fouling  is  the  possibility  of  the 
breaking  of  any  of  the  rails  in  the  fouling  circuit  as  at  "X,"  or 
the  jumpers  4  and  6,  will  render  the  fouling  protection  ineffective 

36 


THE    TRACK    CIRCUIT 


and  would  remain  undetected  until  discovered  either  on  inspec- 
tion or  when  a  car  within  the  fouling-  limits  would  fail  to  de-ener- 
gize the  relay.  In  view  of  this  it  should  be  evident  that  as  far 
as  the  turnout  or  crossing  tracks  are  concerned,  no  broken  rail 
protection  is  provided  in  the  shunt  fouling  scheme. 

In  connection  with  the  description  of  the  shunt  fouling,  atten- 


£ 


FIG.   19. 


FIG.  21. 


tion  will  be  called  to  one  error  which  is  often  committed  when 
laying  out  circuits  of  this  kind  :  that  is  the  placing  of  an  extra 
jumper  for  each  fouling  circuit  and  locating  the  jumper  close  to 
the  insulated  joints  near  the  main  track.  The  object  in  employ- 
ing this  additional  jumper  is  to  provide  against  the  occurrence 
of  the  breaking  of  the  jumper  4,  which  would  render  the  fouling 
circuit  ineffective  and  in  which  case  Jumper  "F"  would  keep  the 
protection  intact.  A  broken  rail  in  the  main  track  at  "Y"  would 
remain  undetected  with  the  employment  of  this  jumper  and  keep 
the  track  relay  energized  through  rail  1,  relay  coils,  rail  5,  jumper 
4.  rail  3,  jumper  "F"  and  rail  5  to  battery.  A  shunt  fouling 
applied  to  a  grade  crossing,  while  it  is  undesirable  to  insulate  the 
frog  rails,  is  illustrated  in  Fig.  19,  and  the  description  of  Fig.  18 
also  applies  to  this  figure. 


FIG.  20. 


A  series  fouling  used  in  connection  with  a  grade  crossing  is 
shown  in  Fig.  20.  A  single  rail  track  circuit  is  employed  and 
only  one  rail  of  the  fouling  circuit  is  connected  in  series  with  the 
main  track  circuit.  It  will  be  noted  that  in  this  circuit  the  break- 
ing of  the  rail  "C"  or  "D"  or  the  disconnection  of  jumpers  "E," 
"F"  and  "G"  will  immediately  be  detected  by  the  dropping  of 

37 


ELECTRIC    LOCKING 


the  track  relay  "B,"  this  being  the  advantage  of  the  employment 
of  series  fouling  protection.  Fig.  21  illustrates  the  series  fouling 
applied  so  as  to  connect  all  the  rails  in  series  with  battery  and 
relay.  This  may  prove  advantageous  where  the  fouling  distance 
is  very  short,  but  for  longer  distances  it  is  not  considered  prac- 
ticable to  develop  the  series  arrangement  this  far.     The  arrange- 


FIG.  22. 


ment  shown  in  Fig.  22  will  be  found  very  suitable  at  places  where 
the  fouling  point  is  of  some  distance  from  the  main  track  and 
where  it  is  desirable  to  connect  both  rails  of  the  fouling  circuit 
in  series  with  the  main  circuit  with  a  limited  use  of  jumpers  and 
insulated  joints.  Here  two  track  relays  and  batteries  are  em- 
ployed and  one  rail  of  each  track  used  as  a  common.  This  may 
be  considered  the  most  favorable  arrangement  for  a  track  condi- 
tion of  this  kind.  The  scheme  of  employing  separate  circuits  for 
fouling  protection  of  grade  crossings  is  similar  to  the  circuit 
shown  in  Fig.  16. 

Fouling  of  Turnouts.     The  fouling  protection  employed  for 
a  turnout  or  the  junction  of  two  main  lines  is  shown  in  Fig.  23. 


FIG.  23. 

A  shunt  fouling  circuit  would  provide  a  very  incomplete  and 
unreliable  protection  for  this  condition,  as  both  tracks  being 
main  tracks  and  the  signals  situated  not  less  than  500  ft.  from  the 
switch,  the  fouling  circuit  would  be  of  too  great  a  length.  A 
series  circuit  as  shown  will  be  very  appropriate.  Here  only  one 
jumper  and  two  insulated  joints  are  employed,  and  both  rails  of 

38 


THE    TRACK    CIRCUIT 

both  tracks  used  for  the  current  from  battery  "A"  to  energize 
relay  "B."'  The  dead  section,  which  is  unavoidable  in  this 
arrangement,  may  vary  in  length  from  15  ft.  to  30  ft.,  depending 
on  the  number  of  frogs  used.  The  short  section,  about  55  ft. 
between  the  switch  point  and  the  dwarf  signal,  may  be  considered 
a  shunt  fouling  to  the  main  circuit  because  these  parts  of  the 
rails  are  not  used  in  the  control  of  the  track  relay. 


FIG.  24. 

Another  arrangement  of  a  track  layout  of  a  similar  kind  is 
shown  in  Fig.  24.  Here  also  a  series  circuit  is  employed,  but  the 
dead  section  is  entirely  removed,  the  insulated  joints  "C"  and 
"D"  being  very  slightly  staggered.  By  placing  the  jumper  as 
shown  the  shunt  fouling  of  the  piece  of  track  between  the  dwarf 
and  the  switch  has  been  confined  to  one  rail  only,  the  other  being 
connected  in  series  with  the  main  circuit.  The  disadvantage  of 
the  circuits  shown  in  Figs.  13  and  14  is  the  necessity  of  the  placing 
of  the  battery  at  one  signal  and  the  looping  around  the  switch  to 
the  relay  at  the  other  signal.  This  arrangement  not  only  necessi- 
tates a  series  track  circuit  of  considerable  length,  but  other  con- 
ditions, such  as  slow  release  of  the  relay  armature,  circuit 
selections,  etc.,  often  make  this  arrangement  undesirable.  In  a 
separate  circuit  fouling  protection  the  battery  should  be  placed  at 
"F"  and  a  track  relay  at  "G"  and  "H." 


Fouling  of  Switches.  The  fouling  protection  required  for 
switches  at  sidings  is  in  many  respects  similar  to  the  arrange- 
ments covered  in  connection  with  main  track  turnouts,  and  the 
three  principal  methods  employed  are  identically  the  same.  At 
places  where  no  section  locking  is  employed  the  simplest  way  to 
take  care  of  switches  is  to  jump  around  the  switch  by  the  use  of 
insulated  points  and  jumpers  as  shown  in  Fig.  12  and  Fig.  25, 
the  first  one  being  applicable  to  single  rail  and  the  latter  to  double 
rail  circuits.     In  Fig.  15  no  insulated  switch  roads  or  connections 

39 


ELECTRIC   LOCKING 

are  necessary,  but  a  dead  section  of  from  33  ft.  to  66  ft.  is  pres- 
ent. With  this  circuit  a  broken  rail  at  "X"  will  not  be  indicated 
by  the  track  relay,  the  current  taking  the  path  as  shown  by  the 
arrows.  The  insulated  joint  "A"  may  be  placed  at  fouling  point 
"A"  and  joint  "B"  and  jumper  "C"  added.  By  this  arrangement 
a  shunt  fouling  is  added  to  the  track  circuit  protection.     Another 


FIG.  25. 

arrangement  giving  very  inadequate  protection  is  that  in  which 
the  switch  rail  is  separated  from  electrical  connection  with  the 
main  rail  by  means  of  wedges  or  wedge  blocks,  but  this  scheme 
is  only  applicable  to  certain  styles  of  electric  locking. 

The    most    common    arrangement    of    fouling    protection    for 


FIG.  26. 


FIG.  27. 


switches  at  interlocking  plants  is  illustrated  in  Fig.  26.  A  shunt 
fouling  protection  is  here  afforded  by  the  use  of  four  insulated 
joints,  a  jumper  and  insulated  front  and  head  switch  roads.  The 
objections  to  the  use  of  the  jumper  "A"  were  covered  in  the 
description  of  Fig.  8. 


A  simple  series  fouling  circuit  is  shown  in  Fig.  27.  It  will  be 
noted  that  the  outside  rail  of  the  sliding  is  connected  in  series  with 
the  main  track  rails.  With  this  arrangement  borken  rail  protection 
is  given  for  the  outside  rail,  this  rail  being  the  most  important 
on  account  of  the  side  strain  imposed  upon  it  with  a  train  moving 
towards  the  switch.     Where  the  track  circuit  terminates  at  or 

40 


THE    TRACK    CIRCUIT 

close  to  the  foiling  point  of  a  siding,  very  favorable  arrange- 
ments of  fouling  protection  can  be  procured  and  without  the 
placing  of  any  insulated  joints  on  the  main  track.  Fig.  28  illus- 
trates perhaps  the  best  possible  arrangement  of  a  series  fouling 
circuit  of  this  kind,  using  the  least  number  of  insulated  joints  and 
having  the  length  of  the  junipers  reduced  to  a  minimum. 


Ladder  Tracks.  When  a  series  of  turnouts  connect  a  straight 
main  track  with  a  number  of  parallel  equally  distant  side  tracks, 
the  whole  arrangement  of  tracks  is  called  a  "ladder  track." 
Ladder  tracks  are  very  commonly  employed  in  large  yards,  and 
a  convenient  way  of  arranging  the  circuits  is  shown  in  Figs.  29 
and  30.  In  Fig.  29  two  turnouts  are  connected  in  series,  while 
the  third  is  provided  with  shunt  fouling  protection.  While  no 
dead  section  is  present  in  this  circuit,  it  does  not  provide  as  much 
protection  as  the  circuit,  Fig.  30.  One  battery  here  supplies  cur- 
rent for  two  relays  and,  of  course,  where  more  turnouts  occur 
in  one  ladder  track,  additional  relays  may  be  connected  in  a  sim- 
ilar manner  with  one  battery.     The  presence  of  a  train  on  any 


FIG.   30. 

parts  of  the  circuit  will,  of  course,  drop  all  the  relays  connected 
in  multiple  with  one  battery,  but  as  no  parallel  movements  are 
possible  this  is  a  good  feature.  It  is  possible  also  to  provide  series 
fouling  with  ladder  tracks,  but  on  account  of  the  number  of  addi- 
tional joints  and  junipers  required  and  the  somewhat  complex 
arrangement  resulting,  this  method  is  not  to  be  recommended. 

41 


ELECTRIC   LOCKING 

Fouling  of  Lap  Switches.  The  shunt  fouling"  of  a  lap 
switch  is  shown  in  Fig.  31.  The  negative  rails  are  indicated  in 
heavy  lines. 


FIG.  31. 

Fouling  of  Crossovers.  Fouling  protection  is  also  required 
for  crossovers  so  that  a  movement  over  it  will  shunt  the  relay  for 
either  one  or  both  tracks.  There  are  two  distinct  ways  of  pro- 
viding fouling  protection  for  a  crossover.  The  one  is,  where  a 
crossover  connects  two  main  tracks,  in  which  case  the  crossover 
is  made  to  shunt  partly  one  and  partly  the  other  track.  The  other 
case  is  where  a  crossover  connects  a  main  and  a  side  track,  in 


FIG.   32. 

which  case  the  crossover  will  shunt  only  with  the  main  track. 
Fig.  32  shows  the  method  of  fouling  protection  most  frequently 
employed  for  a  main  to  main  crossover.  It  will  be  noted  that  this 
circuit  will  come  under  the  class  of  shunt  fouling.  A  car  standing 
on  the  center  of  the  crossovers  between  both  tracks  will  affect  the 
relays  ffor  both  track  circuits.  It  should  be  noted,  however,  that 
with  crossovers  connecting  tracks  of  ordinary  spacing,  complete 
fouling  protection  cannot  be  obtained.  Thus,  it  is  possible  for  a  car 


u — * 

Ar 

"8 

*— — -—-"T 

1                    -     1 

V 

FIG.  33. 


FIG.  34. 


to  partly  stand  on  the  crossover  as  at  "A,"  and  while  thus  fouling 
track  "B,"  will  not  affect  its  track  relay.  A  broken  rail  or  jumper 
in  the  crossover  circuit  will  permit  a  car  to  be  standing  on  the 
circuit  without  affecting  the  track  relay  for  the  track  whose 
fouling  circuit  is  impaired.  A  more  complete  fouling  protection 
is  procured  with  Fig.  33  for  a  main  to  main  crossover,  using  the 

42 


THE    TRACK    CIRCUIT 

scheme  of  series  fouling,  one  rail  of  the  crossover  being  in  series. 
Perhaps  the  highest  development  of  crossover  protection  for 
main  to  main  track  is  illustrated  in  Fig.  34.  Here  a  separate 
circuit  is  used  and  the  fouling  protection  carried  as  far  as  pos- 
sihle  toward  each  track.  A  train  standing  on  either  track  will 
not  affect  the  crossover  relay,  which  will  only  respond  with  a  pair 


f 

♦■ 

Sidma 

<*h       ~i  _ 

. -^ — - — "^- — ■""■ — 

, 

- 

\ 

— — — ' 

Ha  in 

- 

FIG.   35. 

of  wheels  passing  over  the  joints  at  point  "A"  or  "B."  The  cir- 
cuits controlled  through  either  main  track  must  be  carried 
through  crossover  relay  in  order  to  obtain  desired  fouling  pro- 
tection. In  most  cases  the  breaking  of  the  main  track  circuits 
through  the  crossover  relay  will  greatly  simplify  the  circuits 
through  the  plant.  This,  however,  will  necessitate  the  placing  of 
insulated  joints  in  the  main  rail  which,  of  course,  is  undesirable. 
Shunt  fouling  protection  for  one  track  only  where  single  rail 
circuit  is  employed  is  shown  in  Fig.  35.  This  circuit  may  be 
considered  a  very  good  arrangement  with  the  use  of  a  limited 
number  of  insulated  joints  and  jumpers,  and,  as  explained,  a  pair 
of  wheels  passing  joints  "A"  will  shunt  the  main  track  relay. 

Fig.  36  provides  the  same  protection  and  is  in  most  respects 
similar  to  Fig.  35,  with  the  exception  that  the  circuit  is  entirely 
separated    from   adjacent   track   circuits   by   the   employment   of 

D      B 


Siding 


m^ 


FIG.  36. 


insulated  joints  "A"  and  "T>."  While  this  extra  precaution  may 
not  appear  necessary  when  considering  a  single  crossover  be- 
tween two  tracks,  there  are  places  where  the  omission  of  these 
joints  may  cause  complications,  especially  where  other  crossovers 
should  join  the  main  track  with  the  secondary  track,  whether 
directly  or  indirectly.     Transpositions  of  the  track  circuit  for  the 

43 


ELECTRIC    LOCKING 

siding  may  also  be  necessary  if  the  joints  "A"  and  "B"  are  left 
out.  Thus,  on  track  layouts  offering-  complications  in  the  nature 
of  crossovers  and  turnouts  the  employment  of  the  additional  insu- 
lated joints  is  not  only  urgent,  but  very  necessary.  As  previously 
stated,  in  connection  with  shunt  fouling  protection  for  switches, 
the  jumper  "C"  should  be  omitted.  The  circuit  shown  in  Fig.  36 
also  provides  protection  at  places  where  troubles  from  foreign 
current  are  likely  to  occur.  This  will  be  evident  when  consider- 
ing that  a  car  standing  at  "D"  will  allow  foreign  current  to  flow 
towards  the  main  track  circuit  over  jumper  and  may  cause  de- 
rangement of  this  circuit. 

Passing  Center   Track  Crossover.     The   fouling  protection 
of  three  tracks  running  into    two    tracks    is    shown  in  Fig.  37. 


FIG.   37. 

Series  fouling  is  applied  to  this  circuit  and  a  train  approaching 
track  "B"  from  track  "A"  with  switch  "D"  normal  will  shunt 
track  relay  "B,"  as  shown  in  the  figure — "E"  representing  a  pair 
of  wheels.  With  switch  "D"  released  and  a  train  passing  from 
track  "A"  to  "C"  the  track  relay  "C"  should  be  shunted.  Atten- 
tion will  here  be  called  to  one  thing  very  important  to  observe 
when  laying  out  the  track  circuits  at  an  interlocking  plant,  and 
that  is  the  arrangement  of  the  circuits  with  the  object  in  view 
of  maintaining  the  flexibility  of  the  plant  by  permitting  parallel 
movements  to  take  place  simultaneously.  This,  inasmuch  as  the 
signaling  of  a  yard  is  installed  as  much  for  the  acceleration  of 
traffic  as  for  its  protection.  Thus  it  must  be  observed  that  it 
should  be  possible  for  a  train  to  move  from  track  "A"  to  "B" 
over  switch  "D"  normal  without  interfering  with  a  movement 
over  track  circuit  "C."  That  is,  in  the  present  case  the  fouling 
protection  for  either  track  "B"  or  "C"  should  be  so  arranged 
that  if  a  pair  of  wheels  should  bridge  track  "A"  at  "E"  only  the 
track  relay  for  circuit  "B"  should  be  shunted,  while  track  relay 
"C"  should  not  be  affected,  because  a  movement  over  this  track 

44 


THE    TRACK    CIRCUIT 

would  not  be  endangered  in  such  a  case.  The  same  should  ob- 
tain with  the  fouling-  of  track  "C,"  and  a  train  moving  over  track 
section  "B."  This  is  very  effectively  accomplished  in  the  present 
figure  without  much  complication  in  the  track  circuit  arrange- 
ment.   The  other  features  of  this  circuit  are  self-explanatory. 


FIG.   38. 

Fouling  of  Scissors  Crossovers.  One  method  of  insulating 
scissors  crossovers  having  stiff  frogs  is  shown  in  Fig.  38.  The 
circuit  is  arranged  so  that  more  fouling  protection  is  provided  for 
the  main  track  than  the  secondary.  It  should  be  noted  that  shunt 
fouling  is  provided.     In  this,  as  in  other  schemes  of  shunt  foul- 


ly 


ing,  the  additional  jumper  shown  dotted  at  "X"  should  be 
avoided.  Another  method  of  insulating  scissors  crossovers  be- 
tween two  main  tracks  is  shown  in  Fig.  39.  Equal  fouling  pro- 
tection being  desired  for  each  track,  a  dead  section  in  the  frog 
rails  cannot  be  avoided.     Section  "A"  is  dead. 


FIG.  40. 


Movable  Point  Frogs.  The  simplest  way  to  provide  for  the 
continuation  of  a  track  circuit  through  a  movable  point  frog  would 
be  to  transpose  the  circuit  and  jump  around  the  frog  points  as 

In  Fig.  40  no  fouling  pro- 


shown  in  Fig.  11  and  other  figures 


45 


ELECTRIC   LOCKING 

tection  is  employed,  but  joints  "A"  and  "B"  are  placed  in  the 
turnout  rails  to  prevent  a  leakage.  Another  reason  for  placing 
these  joints  as  shown  is  to  prevent  a  broken  rail  at,  for  instance, 
"X"  to  remain  undetected.  This  will  be  evident  when  following 
current  from  positive  side  of  battery  "C,"  positive  rail,  relay 
coils,  negative  rail  to  "X,"  rail  1,  wheels  of  car,  rail  2  and  nega- 


FIG.  41. 


tive  rail,  back  to  battery.     Thus  a  car  on  turnout  and  a  broken 
rail  at  "X"  will  keep  track  relay  energized. 

Series  fouling  of  a  movable  point  frog  is  illustrated  in  Fig.  41. 
As  previously  stated  the  disadvantage  of  a  circuit  of  this  kind 
is  the  location  of  the  extra  joints  in  the  main  track  rails. 


Slip  Switches.  The  existence  of  double  and  single  slip 
switches  within  an  interlocking  often  complicates  an  otherwise 
simple  track  circuit  arrangement.  While  some  roads  entirely 
shunt  out  such  switches  on'acount  of  the  complications  met  with 
when  attempting  to  maintain  a  positive  and  negative  rail  through 
them,  other  roads  are  as  precise  in  their  track  protection  of  these 
switches  as  for  the  crossovers  and  switches.  An  elaborate 
arrangement  of  a  track  circuit  carried  through  a  double  slip 
switch,  where  the  insulating  of  the  switch  has  been  partly  com- 
pleted, is  shown  in  Fig.  42.    Here  the  dead  section  "A"  has  been 


FIG.  42. 

considerably  reduced  by  the  employment  of  four  insulated  joints 
and  insulated  switch  rods.  The  dead  section  will  be  of  30  ft. 
length.  This  circuit  cannot  be  used  in  connection  with  No.  8  and 
No.  10  switches.  It  should  be  noted  that  no  dead  section  is  pres- 
ent with  a  train  moving  from  "M"  to  "X"  or  from  "O"  to  "P." 
This  will  be  apparent  when  comparing  the  thickness  of  the  rails 

46 


THE    TRACK    CIRCUTl 

of  each  piece  of  track  touched  by  the  wheels  of  the  train  passing 
over  them,  heavy  and  light  lines  representing  opposite  polarity 
of  the  track  circuit.  The  single  lines  "B,"  "C,"  "D"  and  "E" 
connecting  the  switch  points  each  represent  the  front  rod,  head 
rod  and  from  two  to  four  tie  rods,  but  in  order  to  simplify  the 
diagram  they  are  shown  in  a  single  line.  Each  one  of  these  rods 
is  insulated  and  the  tie  plates  are  cut  to  prevent  an  electrical  con- 
nection between  rails  H — J  and  K — L.  The  single  lines  F  and 
G  at  the  frog  points  represent  an  equal  number  of  rods  as  at  the 
switch  points,  but  these  are  not  insulated. 

Fig.  43  shows  what  is  perhaps    the    highest    development  of 
double  slip  switch  protection.     No  dead  section  is  present  in  this 


C  S      D    E  FG  8F 


C  B  SC 

FIG.  43. 

circuit  with  the  same  number  of  insulated  joints  as  in  the  previous 
circuit.  The  description  of  Fig.  42  will  also  cover  this  figure. 
In  this  circuit  the  front,  head  and  tie  bars  of  the  frog  points  F 
and  G  are  insulated  and  the  tie  bars  cut.  It  will  be  noted  that 
in  the  diagram  the  switch  rods  "B"  apparently  touch  rail  "D"  at 
the  point  "C."  This  would  short  circuit  the  track  battery  and 
shunt  the  track  relay  by  the  connecting  of  positive  rail  "D"  with 
negative  rail  "E."  This  is  prevented,  however,  by  having  the 
switch  rods  "B"  downset  so  far  below  the  rails  "C"  that  the  rods 
in  either  position  of  the  switch  points  will  not  touch  and  make 
an  electrical  connection.  Thus  the  lines  shown  dotted  represent 
that  part  of  the  switch  rod  which  is  downset.  It  will  be  observed 
that  in  this  circuit,  while  the  complete  lower  part  of  the  switch 
is  of  one  polarity,  the  complete  upper  part  is  of  another.  That 
is,  if  a  line  is  drawn  through  the  switch  from  "H"  to  "J"  the 
parts  of  the  switch  on  each  side  of  the  line  is  of  an  opposite  polar- 
ity. This  is  the  most  ideal  condition  obtainable  with  a  double 
slip  switch,  and  a  train  on  any  part  of  the  switch  will  shunt  the 
track  relay  controlled  by  the  circuit.  It  should  be  understood 
that,  while  the  circuits  just  presented  are  shown  as  applied  to 
movable  center  frogs,  they  are    also    applicable    to    double  slip 

47 


ELECTRIC    LOCKING 


switches  employing  rigid  center  frogs.  It  should  also  be  observed 
that  in  insulating  slip  switches  a  series  circuit  arrangement  which 
would  also  give  broken  rail  protection  is  not  possible  without 
complications  which  would  be  found  prohibitive  in  railroad  work. 

Gauntlet  Tracks.  Where  two  tracks  converge  so  as  to 
occupy  a  space  slightly  greater  than  that  required  by  a  single 
track  they  are  called  gauntlet  or  intervolved  tracks,  and  are  used 
on  tunnels,  bridges,  etc.,  where  the  necessary  space  for  a  double 
track  is  not  available.     Fig.  44  shows    a    gauntlet    track    circuit 


r      + 

>_± — 

-    4- 


FIG.   44. 

arrangement  whereby  only  one  battery  and  relay  is  required.  In 
this  circuit,  if  an  electrical  connection  should  accidentally  be  made 
between  the  two  rails  running  close  together,  as  at  "X,"  the  rails 
between  that  point  and  the  jumper  wires  at  the  end  of  the  sec- 
tion will  be  cut  out  of  the  circuit,  and  consequently  a  broken 
jumper  wire  or  a  broken  rail  at  "Y"  would  not  affect  the  opera- 
tion of  the  track  relay.  The  polarity  of  the  rails  must  be  arranged 
as  shown,  because  if  transposed  a  cross  at  "X"  would  create  a 
battery  short  circuit.  The  best  method  of  arranging  a  gauntlet 
circuit  is  to  provide  two  separate  track  circuits  and  always  have 
like  polarity  on  the  two  rails  closest  together. 

Conclusion.  While  in  the  present  article  d.  c.  track  circuits 
only  have  been  discussed,  without  reference  to  a.  c.  track  cir- 
cuits, it  can  be  said  that  the  arrangement  of  the  latter  will  be 
similar  in  all  cases,  with  the  exception  that  proper  provisions 
must  be  made  for  the  return  of  the  propulsion  current  for  elec- 
tric traction.  A.  c.  single  and  double  rail  circuits  are  in  use,  the 
application  depending  upon  whether  one  or  both  rails  are  given 
up  for  signaling  purposes. 

In  regard  to  track  circuits  in  general,  it  should  be  kept  in  mind 
that  to  connect  a  number  of  long  track  circuits  together,  by  either 

48 


THE    TRACK    CIRCUIT 

taking  battery  for  all  from  a  common  source  of  energy  or  as 
single  rail  circuits,  should  be  strictly  avoided.  This  precaution 
should  be  taken  principally  to  avoid  the  trouble  due  to  foreign 
currents,  and  while  it  may  not  entirely  overcome  the  bad  effects 
from  them,  will  at  least  minimize  their  effects.  Another  reason 
is  the  probability  of  having  a  train  in  one  section  short  circuit 
or  shunt  an  adjacent  track  section. 

From  the  discussion  it  should  be  evident  that  the  question  of 
whether  the  track  circuit  is  extended  to  detect  broken  rails  or  not 
enters  very  much  into  the  decision  of  what  kind  of  track  circuit 
to  employ.  Strict  attention  must  also  be  given  to  the  effect  that 
various  failures  may  have  upon  the  circuits,  such  as  crossed 
wires,  broken  rails,  defective  insulations,  broken  bonding,  poor 
wheel  contact,  low  ballast  resistance,  battery  failures  and  numer- 
ous others.  All  such  failures  must  be  taken  into  account  when 
designing  the  circuits  so  that  no  dangerous  conditions  will  ensue 
without  readily  attracting  the  attention  of  the  maintainer.  In 
that  way  only  can  perfect  safety  be  insured. 


49 


Ill 

TRAP    CIRCUITS 

General.  A  "dead"  section  is  a  section  of  track  where  no 
track  circuit  can  be  maintained,  and  its  presence  is  a  frequent 
occurrence  in  a  track  circuit  proposition.  It  may  often  be  of 
considerable  length  and  is  caused  at  bridges  or  trestles  which, 
being  built  of  steel,  are  constructed  so  as  to  receive  the  rails 
without  the  intervening  wooden  ties.  It  is  also  caused  at  places 
where  steel  ties,  for  some  reason,  are  employed,  or  where  a  num- 
ber of  streets  cross  a  railroad,  a  railroad  crossing  another,  or 
any  place  where  conditions  prevent  the  proper  maintenance  of  a 
continuous  track  circuit.  In  order  to  protect  such  places  the  only 
alternative  is  to  employ  a  trap  circuit  for  the  safeguarding  of 
train  movements. 

A  trap  circuit  is  really  one  type  of  a  stick  relay  circuit  in  which 
the  rails  generally  are  used  as  a  control  circuit;  but  when  in  all 
cases  a  strictly  automatic  operation  of  the  relay  is  secured  by 
the  movement  of  trains  acting  as  an  actuating  medium  without 
the  contributory  manual  control  of  any  parts  of  the  circuit  or 
devices.  These  types  of  track  circuits  are  also  employed  in  elec- 
tric locking  on  account  of  offering  a  more  economical  installation 
problem,  particularly  in  places  where  no  continuous  track  circuit 
arrangement  is  desired.  In  a  trap  circuit  one  or  more  stick  re- 
lays are  employed  for  the  purpose  of  making  or  breaking  a  circuit 
either  with  the  intention  of  locking  up  a  route  or  preventing  the 
auto  or  semi-automatic  clearing  of  a  signal ;  in  either  case,  pre- 
venting a  train  from  proceeding  until  a  preceding  train  has  passed 
the  dead  section.  It  is  also  employed  in  crossing  bell  circuits  to 
keep  a  bell  in  action  until  the  streets  compelling  the  dead  section 
have  been  passed  by  the  train.  A  trap  circuit  will  necessarily 
consist  of  two  mediums  through  which  the  locking  and  the  re- 
lease of  the  stick  relay  is  effected,  and  these  may  either  be  track 
instruments  or  track  circuits. 

Trap  circuits  for  single  and  double  track  roads  should  be 
arranged  alike  so  that  the  protection  will  take  place  with  traffic 
running  in  either  direction.  This  is  necessary  because,  not  only 
should  movements  with  the  current  of  traffic  be  protected,  but 
also  back-up  movements  and  possible  movements  against  current 
of    traffic.      Circuits   are    employed,    however,    on    double    track 

50 


TRAP    CIRCUITS 

roads  which  only  take  care  of  the  protection  of  movements  with 
the  current  of  traffic.  On  some  types  of  trap  circuits  the  arrange- 
ments for  the  protection  of  traffic  for  movements  in  one  direc- 
tion will  have  to  be  duplicated  if  protection  for  opposing  move- 
ments is  desired.  While  the  figures  are  arranged  showing  a 
draw-bridge  as  necessitating  a  dead  section,  it  is  evident  that  it 
may  constitute  any  condition  previously  described. 


XI 


zn_ 


A 


~C4J 


4MJ 


FIG.  45. 

Track  Instrument  Arrangement.  A  trap  circuit  actuated 
by  the  means  of  two  track  instruments  is  shown  in  Fig.  45.  This 
circuit  is  a  normally  energized  stick  relay  scheme,  and  the  track 
instruments  employed  are  one  having  a  normally  closed  contact 
at  the  starting  end  "A"  and  one  having  a  normally  open  contact 


7 


m 


FIG.  46. 


at  the  releasing  end  "D."  The  operation  is  as  follows:  A  train 
moving  in  the  direction  of  the  arrow  will,  upon  reaching  track 
instrument  "A,"  actuate  this,  thereby  de-energizing  stick  relay 
"1),"  which  will  remain  de-energized  until  the  train  has  reached 
the  releasing  track  instrument  "I!,"  when  relay  "D"  will 
again  pick  up,  through  wires   1,  track  instrument  "A,"  wire  2, 

51 


ELECTRIC   LOCKING 

instrument  "B,"  wires  3  and  4  to  battery.  It  will  stay  picked  up 
through  wires  1,  2  and  4,  its  own  front  point,  and  wires  5  and  6 
to  battery.  The  control  of  the  protective  circuits  will,  of  course, 
be  through  the  front  point  "E."  Fig.  46  shows  the  scheme  as 
applied  to  a  normally  de-energized  stick  relay.  The  starting 
instrument  "A"  will  here  cause  the  energization  of  the  stick  re- 
lay "D"  and  the  stick  relay  will  again  become  de-energized  upon 
the  train  reaching  track  instrument  "B."  It  is  to  be  noted  that 
the  circuits  Figs.  45  and  46  will  give  protection  for  movements  in 
one  direction  only,  and  if  protection  for  both  directions  is  desired 
another  relav  and  set  of  track  instruments  are  necessary. 


Track  Circuit  Arrangement. 

Effective  in  One  Direction.  A  trap  circuit  employing 
track  circuits  as  actuating  mediums,  and  where  protection  is  pro- 
vided for  one  direction  only,  is  shown  in  Fig.  47.     "A"  and  "B" 


-03 


I 


X 


T2 


? 


1 


D-=- 

T     7 


^Sj 


FIG.   47. 

are  pick-up  and  cut-out  sections,  respectively,  and  each  section 
or  rail  is  from  15  ft.  to  30  ft.  in  length.  This  figure  has  a  track 
circuit  which  is  actuated  and  is  in  its  operation  the  same  as  an 
ordinary  track  circuit,  and  entirely  independent  of  the  stick  relay 
circuit.  While  a  train  is  in  the  dead  section  on  the  bridge  the 
track  relay  will,  of  course,  pick  up  again.  It  will  be  observed 
that  insulated  joints  and  jumpers  cut  the  dead  section  (a  draw- 
bridge is  used  in  all  the  diagrams  as  an  illustration)  entirely 
out  of  the  track  circuit.  A  separate  battery  is  in  this  scheme 
used  for  the  operation  of  the  stick  relay  "C."  The  circuit 
operates  as  follows :  A  train  moving  in  the  direction  of  the  arrow 
will,  when  passing  into  section  "A,"  energize  relay  "C"  by  cur- 
rent flowing  from  battery  "D,"  track  connection  1,  wheels  and 
axles  of  train,  rail  2,  jumper  3,  rail  4,  track  connection  5,  coils 
of  stick  relay  "C"  and  wire  6  to  negative  side  of  battery.  When 
the  stick  relay  is  thus  picked  up  it  will  remain  so  through  wire 

52 


TRAP    CIRCUITS 

7 ,  its  own  front  point,  wire  8,  coils  of  relay  and  wire  6  back  to 
battery.  With  the  train  entering  section  "B"  the  current  is 
shunted  out  of  the  relay  through  wire  7,  its  own  front  point  and 
wires  8  and  5,  wheels  and  axles  of  train  and  wires  9  and  6.  It 
should  be  noted  that  in  this  scheme  all  circuit  breaking  through 
the  track  relay  should  also  break  through  a  back  point  of  the 
stick  relay  "C."  Like  all  open  circuit  schemes,  the  present  cir- 
cuit is  susceptible  to  derangements  characteristic  of  such  circuit 
arrangements,  and  cannot  be  classed  as  perfectly  reliable  under 
all  conditions.  An  open  circuit  scheme  is,  as  previously  discussed, 
based  on  the  wrong  principles,  as  there  is  nothing  to  give  assur- 
ance that  the  stick  relay  will  perform  the  duty  to  which  it  is 
assigned.  For  example,  a  break  in  a  wire  would  impair  its  use- 
fulness.    The  relay,  being  normally  de-energized,  will,  of  course, 


1 


TT 


* 


3 


r-1 


S-u-T  y,i*g 


£ 


n 


IS 


FIG.  48. 


(fleet  a  saving  in  the  battery  consumption.  By  controlling  the 
bridge  shunt  wires  through  the  stick  relay,  the  trap  circuit  will 
also  keep  the  track  relay  down  while  the  stick  relay  is  energized. 
Another  trap  circuit  taking  effect  only  when  trains  move  in  one 
direction  is  shown  in  Fig.  48.  A  train  moving  in  the  direction  of 
the  arrow  will,  when  entering  into  section  "A,"  shunt  track  relay 
"C"  and  stick  relay  "D"  through  the  following  circuit :  From 
battery  "F,"  wires  1  and  2,  track  connection  3,  rail  4,  wheels  and 
axle  of  train,  rail  5,  track  connection  6,  wire  7,  front  point  of  re- 
lay "F,"  wires  8  and  9,  front  point  of  relay  "D"  and  wire  10  back 
to  battery.  Relays  "C"  and  "D"  remain  de-energized  until  the 
train  has  entered  section  "B"  and  dropped  relay  "E"  for  this  sec- 
tion. Relay  "C"  will  not  pick  up  until  relay  "D"  is  energized,  for 
the  reason  that  with  relay  "D"  dropped,  battery  positive  is  applied 

53 


ELECTRIC    LOCKING 

to  both  rails  in  track  circuit  "A,"  one  rail  being  fed  directly  from 
baltery  through  track  connection  3  and  the  other  rail  through 
back  point  of  relay  "D"  and  track  connection  6.  Relay  "D"  will 
pick  up  through  circuit  from  battery  "E,"  wires  1  and  2,  coils  of 
relay  "D,'7  wires  8  and  11,  back  point  of  relay  "E"  and  wire  12 
to  negative  side  of  battery.  Relay  "D"  stick-up  circuit  is  as  fol- 
lows :  Battery  "F,"  wires  1  and  2,  coils  of  relay  "D,"  wire  9,  front 
point  of  relay  "D"  and  wire  10  to  battery.  Relay  "C"  is  shunted 
on  back  points  of  relays  "D"  and  "E"  for  cross  and  foreign  cur- 
rent protection.  Relay  "C"  will  pick  up  after  train  is  out  of  sec- 
tion "B,"  and  relay  is  energized  through  the  following  circuit: 
Battery  "F"  wires  1  and  2,  track  connection  3,  rail  4,  coils  of 
relay  "C,"  rail  5,  track  connection  6,  wire  7,  front  point  of  relay 
"E,"  wires  8  and  9,  front  point  relay  "D"  and  wire  10  back  to 
battery.  While  a  broken  rail  in  this  circuit  will  not  prevent  the 
picking  up  of  stick  relay  "D,"  it  will  prevent  the  picking  up  of 
track  relay  "C." 


zc; 


X: 


i — i  3, ..& 


^L 


a. 


~^i 


— D 


> 


FIG.  49. 


Effective  in  Both  Directions.  A  trap  circuit  employing  a 
.ormally  energized  stick  relay  is  illustrated  in  Fig.  49.  Single 
rail  sections  "A"  and  "B"  are  release  and  pick-up  sections  for 
stick  relay  "D,"  the  function  of  each  section  depending  upon  the 
direction  of  the  train  movement.  Each  of  these  sections  can  be 
from  15  ft.  to  30  ft.  in  length.  The  operation  of  the  track  cir- 
cuit is  as  follows : 

A  train  moving  in  the  direction  of  the  arrow  will,  upon  passing 
section  "A"'  and  entering  section  "C,"  shunt  relay  "D,"  which 
will  not  pick  up  again  until  the  train  has  reached  section  "B," 
when  current  will  flow  from  track  battery  "E,"  track  connection 
4,  coils  of  stick  relay  "D,"  track  connection  5,  rail  6,  wheels  and 
axles  of  train,  rail  7,  jumper  8  and  rail  9  back  to  battery.  This 
will  energize  the  stick  relay,  which  will  remain  picked  up  through 

54 


TRAP    CIRCUITS 


the  former  circuit  and  jumper  10,  front  point  of  relay  "D"  and 
track  connection  11.  A  movement  in  the  opposite  direction  will 
have  the  same  effect,  wire  12  connected  to  rail  in  section  "A"  then 
being  used  for  pick-up  purposes. 

The  circuit  shown  in  Fig.  49  is  a  very  simple  and  effective  trap 
circuit,  only  employing  one  line  wire  and  the  track  relay  being 

-  A  — f- B  A 


n-4 


f 


: 


n 


a 


m 


i* 


FIG.  50. 

utilized  as  a  stick  relay.  The  trap  circuit  scheme  employed  in 
Fig.  50  is  similar  to  the  one  shown  in  Fig.  49.  In  the  present 
figure,  however,  an  extra  relay  is  employed  as  a  stick  relay,  and 
through  this  relay  the  regular  track  relay  is  controlled,  so  that 
as  long  as  the  stick  relay  is  down  the  track  relay  will  also  remain 
de-energized.  In  this  way  more  protection  can  be  procured  than 
is  possible  in  Fig.  49,  where  the  stick  relay  will  protect  the  dead 


FIG.  51. 

section  ;  while  in  Fig.  50  the  whole  block  can  be  protected.  "F" 
is  a  protective  shunt  contact  for  the  track  relay  while  the  stick 
relay  is  de-energized.  Sections  "A,"  "B,"  "C"  and  "D"  are  from 
15  ft.  to  30  ft.  in  length.  From  the  description  of  previous  fig- 
ures this  circuit  should  be  readily  understood. 

The  trap  circuit  shown  in  Fig.  51   employs  two  stick  relays, 

55 


ELECTRIC   LOCKING 


also  functioned  as  track  circuit  relays,  and  two  track  batteries. 
Advance  sections  "A"  and  "B"  are  each  from  30  to  60  feet  long. 
Assuming  a  train  to  be  moving  in  the  direction  of  the  arrow, 
first  entering  section  "A,"  it  will  proceed  into  section  "C"  and 
shunt  the  relay  "E"  for  this  section.  After  the  train  has  passed 
the  bridge  and  proceeded  into  section  "D,"  thereby  dropping  re- 
lay "F"  for  section  "D,"  the  back  point  "G"  will  be  closed,  which 
will  complete  the  pick-up  circuit  for  relay  "E"  as  follows :  From 
positive  side  of  track  battery  "H,"  rail  1,  track  connection  2,  wire 
3,  back  point  "G,"  jumpers  4  and  5,  coils  of  relay  "E,"  track  con- 
nection 6  and  rail  7  back  to  battery.  Relay  "E,"  being  a  stick 
relay,  is  held  energized  through  the  former  circuit  and  its  own 
front  point  "K."  Relay  "F"  will  remain  de-energized  until  the 
train  has  completely  passed  out  of  section  "D"  and  moving  in 
section  "B,"  when  it  is  picked  up  by  track  battery  "J,"  through 
rail  8,  reaching  connection  9,  coils  of  relay  "F,"  wire  10,  rail  11, 
wheels  and  axles  of  train  and  rail  12  to  battery.  This  relay  also 
is  held  energized  through  one  of  its  own  points.  The  same 
operations  will  take  effect  if  a  train  moves  in  the  opposite  direc- 
tion to  the  one  just  explained. 

The  circuit  Fig.  52  employs  one  track  relay,  also  functioned 
as  a  stick  relay,  and  advance  sections  which  serve  as  pick-up  cir- 


* 


C±=  B 


i 


n 


3 


n. 


D^J 


E 


FIG.  52. 

cuits.  These  advance  sections  can,  of  course,  be  of  any  reason- 
able length.  A  train  moving  in  the  direction  of  the  arrow  will 
shunt  the  stick  relay  "E"  through  the  following  circuit :  From 
positive  side  of  battery  "D,"  rail  1,  jumper  2,  rail  3,  track  con- 
nection 4,  wire  5,  front  point  of  relay  "A,"  wire  6,  back  point  of 
relay  "C,"  wire  7,  coils  of  relay  "E,"  track  connection  8,  rail  9, 
jumper  10  and  rail  11  back  to  battery.  The  stick  relay,  after  the 
train  has  passed  out  of  section  "C,"  will  stick  through  one  of  its 
own  points.  The  same  will  take  effect  upon  a  train  moving  in 
the  opposite  direction. 

56 


TRAP    CIRCUITS 


Fig.  53  shows  another  trap  circuit  using  a  track  relay,  which 
is  also  employed  as  a  stick  relay.  A  train  moving  in  the  direction 
of  the  arrow  will,  upon  reaching  section  "B,"  drop  stick  relay, 
and  when  train  has  entered  into  section  "C"  this  relay  will  pick 
up  through  hack  point  of  track  relay  "C"  and  stick  up  through 
its  own  point. 

Precautions  ix  Desigx.  In  regard  to  trap  circuits  in  general 
the  following  should  be  observed  when  they  are  applied  for  elec- 
tric locking  purposes :  When  a  trap  circuit  is  applied  independ- 
entlv  of  the  track  circuit,  as,  for  instance,  in  Fig.  47,  it  is  obvious 
that,  while  a  train  when  entering  onto  track  section  B  will  re- 
lease the  trap  circuit  and  consequently  the  locking  effected  by  it, 
the  distance  between  this  section  and  the  bridge  must  be  longer 


& 


3: 


i 


-w 


I3_ 


u 


m 


FIG. 


than  the  longest  train  expected  to  traverse  the  route.  Should  it 
be  impossible  to  locate  the  releasing  track  section  or  track  instru- 
ment at  a  distance  far  enough  from  the  crossing  to  accommodate 
long  trains,  the  lock  used  in  the  electric  locking  must  also  be 
controlled  through  some  track  circuit  medium  which  will  prevent 
the  unlocking  of  the  route  until  the  train  has  passed  out  of  the 
dead  section  or  whatever  condition  the  trap  circuit  was  installed 
to  protect. 

A  trap  circuit  installed  for  the  locking  and  release  of  an  elec- 
tric locking  arrangement  can  have  the  length  of  the  release  and 
locking  track  sections  as  specified  in  the  description  of  the  various 
schemes.  As  this  distance  is  in  all  cases  never  made  shorter  than 
a  rail  length,  and  while  proper  for  an  electric  locking  proposition. 
it  must  be  made  shorter  where  a  trap  circuit  is  also  employed  for 
the  semi-automatic  control  of  signals.  The  length  of  the  lock- 
ing and  release  sections  must  not  be  sufficient  to  allow  a  car  to 
stand  in  either  of  these  sections  without  affecting  the  signals. 
Hence,  in  most  cases,  to  insure  full  protection,  it  will  be  necessary 
to  cut  the  rails  at  each  circuit  to  provide  shorter  sections. 

57 


IV 
INDICATION   LOCKING 

Definition.  The  nomenclature  "Indication  Locking"  has  been 
defined  by  the  Railway  Signal  Association  as  being :  Electric 
Locking  adapted  to  prevent  the  manipulation  of  levers  which 
would  bring  about  an  unsafe  condition  in  case  a  signal,  switch 
or  other  operated  device  fails  to  make  a  movement  corresponding 
with  that  of  the  operating  lever ;  or,  adapted  directly  to  prevent 
the  operation  of  one  device  in  case  another  device,  to  be  operated 
first,  fails  to  make  the  required  movement. 

For  a  correct  conception  of  the  advantages  derived  from  the 
use  of  indication  locking  and  the  grave  necessity  for  its  employ- 
ment in  connection  with  power  operated  units,  the  reader  should 
bear  in  mind  the  great  difference  existing  between  the  control 
and  operation  of  a  mechanical  and  a  power  unit. 

Dog  Locking  Protection.  There  are  certain  features  which 
are  common  to  all  interlockings,  namely,  the  arrangement  of  the 
mechanical  locking  in  the  machine.  That  is,  the  levers  for  the 
operation  of  the  signals  and  switches  are  so  interconnected 
through  the  mechanical  locking  between  them  that  their  manipula- 
tion can  only  occur  in  predetermined  sequence,  and  in  this  way 
it  is  insured  that  only  proper  and  non-conflicting  routes  can  be 
set  up  for  the  movement  of  trains.  With  the  reversal  of  the  home 
signal  lever  all  the  switch  and  lock  levers  in  the  route  over  which 
the  signal  governs  are  locked  in  their  normal  or  reversed  position, 
as  the  conditions  require,  and  all  opposing  signal  levers  locked  in 
their  normal  position,  thus  effectively  preventing  the  operator 
from  reversing  a  lever  either  by  mistake  or  inadvertence,  which 
would  cause  the  display  of  conflicting  and  dangerous  signal  in- 
dications. Thus,  as  far  as  levers  are  concerned,  in  neither  me- 
chanical nor  power  interlockings  can  two  opposing  signals  be  dis- 
played simultaneously. 

Indication  for  Mechanically  Operated  Signal.  With  the 
use  of  pipe  or  wire  connected  signals  at  a  mechanical  plant,  there 
can  be  no  doubt  of  their  being  thrown  in  accordance  with  the 
movement  of  the  lever  as  the  operator  can  readily  ascertain 
whether  a  signal  has  performed  the  operation  intended,  or  test 

58 


INDICATION    LOCKING 

the  integrity  of  the  connection  between  the  lever  and  the  function 
by  the  "feel"'  of  the  lever.  Should  any  obstruction  prevent  the 
signal  from  assuming  the  stop  position,  a  failure  of  this  kind 
would  also  prevent  the  lever  from  being  placed  in  the  complete 
normal  position  and  consequently  keep  the  route  governed  by  the 
signal  locked  up  by  the  mechanical  locking.  Furthermore,  the 
signal  blade  and  spectacle  casting  are  constructed  so  they  are 
thrown  by  a  powerful  force  and  with  sufficient  inertia  to  remove 
a  retardation,  and  any  breakage  of  connections  will  cause  the 
signal  to  assume  the  stop  position.  Again,  by  arranging  the 
cranks  used  in  the  operation  so  that  the  blade  is  pushed  to  the 
clear  position  instead  of  pulled,  the  accidental  buckling  of  the 
pipe  line  will  prevent  the  signal  from  assuming  a  clear  position 
with  the  lever  normal. 

Indication  for  Mechanically  Operated  Switches.  The 
conditions  which  obtain  with  regard  to  the  operation  of  switches 
at  a  mechanical  plant  are  somewhat  different,  as  the  possibility 
of  the  pipe  lines  breaking  or  buckling  enough  to  allow  the  lever 
to  be  put  in  the  full  reversed  position  with  the  switch  only  partly 
reversed  must  be  seriously  considered.  For  this  reason  some 
form  of  locking  is  necessary  and  this  is  accomplished  in  two  ways : 
by  the  facing  point  lock  and  by  the  switch  and  lock  movement  in 
conjunction  with  the  bolt  lock.  The  facing  point  lock  is  operated 
independently  of  the  switch  and  by  a  separate  lever,  the  full 
reversal  of  this  lever  giving  assurance  that  the  switch  has  entirely 
completed  its  movement.  Thus  it  may  be  said  that  the  indication 
locking  for  a  switch  at  a  mechanical  interlocking  plant  consists  in 
the  ability  of  the  operator  to  force  a  plunger  which  slides  in  a 
fixed  casting  through  a  hole  in  a  sliding  bar,  which  bar  is  fastened 
to  and  moves  in  unison  with  the  switch  points.  If  for  any  reason 
the  switch  points  do  not  go  to  the  proper  place  when  the  lever  by 
which  the  switch  is  operated  is  thrown,  it  is  obvious  that  the 
plunger  cannot  be  thrust  through  the  hole  in  the  sliding  bar  and 
the  switch  cannot  be  locked,  thus  indicating  to  the  leverman  that 
the  switch  is  not  in  a  proper  position. 

Power  Opkrated  Units.  With  a  power  operated  unit,  the 
conditions  are  vastly  different.  Here  by  the  use  of  electricity  or 
any  other  form  of  power  for  the  operation  of  the  units  the  more 

59 


ELECTRIC   LOCKING 

immediate  control  is  transferred  from  the  operator,  who  by  the 
manipulation  of  the  lever  is  merely  causing  the  make  or  the  break 
of  a  contact  through  which  the  unit  is  being  operated.  There- 
fore, it  is  not  safe  to  depend  upon  the  assumption  that  a  unit  has 
responded  to  a  given  lever  movement  and  taken  a  position  cor- 
responding with  the  movement  of  the  lever,  as  the  circuit  may 
be  open  at  any  one  of  a  number  of  places  so  that  current  will 
not  reach  the  unit  at  all,  or  the  movement  of  a  switch  may  be 
obstructed  so  that  the  motor  or  other  actuating  device  is. unable 
to  operate  it.  Thus,  indication  locking  is  considered  a  very  neces- 
sary adjunct  to  all  interlocking  plants  employing  electricity  or 
other  kinds  of  power  as  an  operating  medium. 

When  the  Indication  Should  Be  Effective  for  a  Signal. 
A  danger  failure  of  a  signal  is  the  term  applied  when  a  signal 
lever  has  been  reversed  for  the  clearing  of  the  signal  while  the 
signal  is  sticking  in  the  stop  or  danger  position.  A  clear  failure 
is  the  condition  when  a  signal  is  sticking  clear  with  the  placing 
of  the  lever  normal.  A  clear  signal  failure  is  the  only  failure 
that  may  be  called  dangerous  and  the  only  kind  that  indication 
locking  should  protect  against.  That  no  indication  as  to  the 
proper  operation  of  a  signal  is  needed  with  reversal  of  a  lever 
for  the  clearing  of  a  signal  should  be  obvious,  for  the  reason  that 
if  such  a  failure  should  occur  the  signal  would  display  the  stop 
indication.  The  need  of  an  indication  as  to  the  condition  of  the 
signal  is  only  urgent  with  the  placing  of  the  lever  in  the  normal 
position,  because  by  such  a  move  the  release  of  the  switch  levers 
for  the  route  is  accomplished  and  the  operator  is  at  liberty  to  set 
up  an  opposing  route.  Before  this  can  occur  it  is  evident  that  in 
order  to  prevent  the  operator  from  displaying  a  clear  signal  per- 
mitting a  certain  train  movement  while  at  the  same  time  another 
signal  permitting  a  conflicting  movement  is  sticking  clear  (a 
condition  which  may  cause  a  wreck  or  derailment  or  the  devia- 
tion of  a  train  from  its  proper  course),  it  must  be  assured  that 
no  two  opposing  clear  signals  can  be  displayed  simultaneously. 

An  indication  lock  when  applied  to  a  signal 

(1)  Will  inform  the  operator  whether  or  not  a  signal  has 
responded  to  a  given  lever  movement  and  hence  assist  in  detect- 
ing an  improper  clear  indication  of  a  signal,  or,  in  other  words, 
prevent  a  clear  failure. 

60 


IX  D1C  A  TION    LOCK  IXC 

(2)  Will  prevent  the  placing  of  the  signal  lever  upon  which 
it  is  located  at  full  normal  and  the  consequent  unlocking  of  the 
switch  levers  in  the  route  governed  by  the  signal,  unless  the  sig- 
nal has  assumed  the  stop  or,  in  the  case  of  a  distant  signal,  the 
caution  position. 

When  the  Indication  Should  be  Effective  fob  a  Switch. 
The  function  of  an  indication  lock  when  applied  to  a  switch  lever 
must  necessarily  be  to  prevent  the  unlocking  of  the  lever  in  its 
normal  and  reverse  positions  unless  the  switch  has  followed  the 
movement  of  the  lever  and  has  assumed  and  is  locked  in  a  cor- 
responding position. 

An  indication  lock  when  applied  to  a  switch 

(1)  Will  inform  the  operator  whether  a  switch  has  responded 
to  a  given  lever  movement  and  assumed  a  position  corresponding 
with  the  position  of  the  lever  by  which.it  is  controlled. 

(2)  Will  prevent  the  clearing  of  a  signal  governing  train 
movements  over  the  switch  unless  the  switch  is  in  the  proper  and 
locked  position,  and  also  prevent  the  lining  up  of  conflicting 
rontes  until  it  has  assumed  its  safe  and  proper  position. 

Development  of  Electric  Indication  Locking.  The  first 
thought  that  would  occur  to  anyone  attempting  to  solve  the  prob- 
lem of  an  indication  or  automatic  release  of  the  locking  when 
power  is  used  in  the  operation  of  an  interlocked  unit  would  be  to 
employ  the  main  source  of  current  used  in  operating  the  plant 
for  energizing  the  indication  magnet  and  have  the  unit  operating 
mechanism  close  a  controller  completing  the  indication  circuit  at 
the  proper  time.  In  fact,  the  first  installations  ever  made  had  the 
circuit  for  the  indication  lock  arranged  as  shown  in  Eigs.  54  and 
55.  These  diagrams  are  simplified  and  all  contacts  not  essential 
to  the  principles  involved  in  this  indication  scheme  have  been 
omitted.  Fig.  54  shows  a  signal  indication  circuit,  and  it  will  be 
noted  that  the  indication  lock  takes  battery  at  the  coils  and  goes 
to  battery  common  through  a  circuit  controller,  on  the  signal, 
closed  in  the  normal  position.  In  this  scheme,  however,  a  cross 
at  "X"  between  the  two  control  wires  will  cause  a  false  indica- 
tion, as  it  will  have  the  same  effect  as  the  closing  of  the  indication 
contact  at  the  signal,  and  an  indication  will  be  produced  with  the 
signal  at  clear.  Fig.  55  shows  a  switch  indication  circuit,  being 
divested  of  the  apparatus  and  circuit  controllers  not  directly  con- 

61 


ELECTRIC   LOCKING 

cernecl  in  the  formation  of  the  indication  circuits.  With  the  com- 
plete reversal  of  the  switch,  the  circuit  closer  C,  actuated  by  bar 
B,  which  is  connected  to  the  switch  point  or  preferably  to  the 
lock  bar,  will  bridge  contacts  D  and  E  and  close  the  reverse  indi- 
cation circuit.  This  circuit  will  Mow  from  battery  positive 
through  reverse  indication  lock  R,  reverse  indication  wire  RI, 
contact  D,  C,  and  E  to  common.     This  would  permit  the  final 


YV\lnd  noaq.   !         Circuit  breaker _    •    Lei,er    Ind  locks       RI 
1  Stl  *    !    v     on  signal.  f  ^ | ; 


i 


0    E 


N.l. 


-r-* T 


FIG.   54. 

t 


FIG.  55. 


-» — «- 


*M 


nr* — 


^rf 


J- 


Ind  mag. 


'•      Signal  rnotor\\ 
:  Circuit  breaker - 


FIG.  56. 


FIG.  57. 


movement  of  the  lever  to  take  place.  The  mere  inspection  of  this 
diagram  will  readily  display  the  grave  dangers  of  this  scheme. 
An  accidental  cross  of  the  RI  and  common  wire  at  X  will  have 
the  same  effect  as  the  bridging  of  contacts  D  and  E  at  the  switch. 
Thus,  an  indication  would  be  given  irrespective  of  the  position  of 
controller  C,  and  consequently  irrespective  of  the  position  of  the 
switch.  Such  a  cross  can  in  practice  easily  happen  through  faulty 
insulation,  and  the  grounding  of  either  RI  or  XI  wire  will  have 
the  same  effect  as  the  mentioned  cross. 


Safety  and  Reliability  of  Indication.  To  insure  a  reliable 
and  adequate  indication  for  an  interlocking  system  it  should  be 
observed  that : 

(a)  The  power  for  actuating  the  indication  magnet  is  pro- 
cured at  the  unit  operated. 

(b)  A  number  of  predetermined  things  should  occur  in 
proper  sequence  in  addition  to  the  regular  lever  movements,  and 
this  preferably  within  a  certain  time  limit,  before  the  indication 
release  is  effected. 

(c)  The  effect  of  a  cross  or  a  ground  of  the  indication  wire 
should  -tend  to  prevent  instead  of  cause  an  indication. 

62 


IX  DIC  AT  ION   LOCKING 

(&)  In  order  to  prevent  two  levers  operated  simultaneously 
from  receiving  an  indication  caused  by  crossed  wires  while  only 
one  of  the  functions  has  performed  the  operation  intended,  it 
should  be  assured  that  the  current  emanating"  from  one  function 
for  indication  purposes  should  be  subjected  to  return  to  that  func- 
tion, thereby  hindering  the  indicating  current  from  taking  mul- 
tiple paths  through  the  devices  and  cause  false  indications  through 
a  single  cross. 

Indication  at  Mechanical  Interlocking.  There  are  at 
present  two  ways  in  which  the  indication  may  be  performed  for 
power  operated  signals  at  mechanical  plants,  and  these  are : — 

(1)    By  Battery  indication,  and  (2)  by  Dynamic  indication. 

In  the  battery  indication  scheme,  the  unlocking  of  the  lever  is 
effected  either  directly  by  the  closing  of  a  contact  at  the  signal 
with  the  blade  in  normal  position,  thereby  completing  a  circuit 
which  will  send  current  through  the  indication  lock  magnet ;  or, 
it  may  also  be  effected  in  an  indirect  way  in  combination  with 
route,  stick  or  approach  locking,  in  which  case  the  closing  of  a 
contact  with  the  blade  in  the  normal  position  will  pick  up  a  stick 
relay  or  a  signal  indicator,  and  this  in  turn  close  a  contact  which 
will  effect  the  energization  of  the  indication  lock  magnet.  Fig. 
56  shows  the  battery  indication  scheme  applied  to  a  home  and 
a  distant  signal,  and  it  is  to  be  noted  that  the  principles  are  the 
same  as  covered  in  Fig.  54  with  this  exception  :  In  Fig.  56  the 
source  of  indication  is  carried  out  to  the  signal  and  battery  com- 
mon connected  directly  at  the  indication  magnet.  A  cross  will 
here  prevent  an  indication  and  call  the  operator's  attention  to  its 
presence  by  his  inability  to  complete  the  stroke  of  the  lever.  The 
lock  permits  the  placing"  of  the  lever  as  far  as  the  normal  latch- 
ing position,  so  that  with  the  movement  of  the  home  lever  toward 
normal  the  indication  current  will  flow  from  battery  at  the  signal 
circuit  breaker  on  distant  arm  1,  circuit  controller  on  home  signal, 
lever  latch,  coils  of  indication  lock  to  battery  negative.  Thus,  in 
order  to  energize  the  indication  lock  it  will  be  observed  that  the 
distant  signal  must  be  in  the  caution  and  the  home  signal  in  the 
normal  position.  In  order  to  save  current  and  also  to  prevent 
the  dangers  caused  by  residual  magnetism,  the  contact  controlling 
the  indication  lock  is  only  made  while  the  lever  is  being  manipu- 
lated.    While  the  purpose  of  an  indication  lock  is  to  prevent  tin 

63 


ELECTRIC   LOCKING 

placing  of  the  lever  controlling  a  signal  normal  while  the  signal 
is  displaying  a  clear  indication,  it  is  equally  important  that  the 
lock  is  so  constructed  that  the  leverman  is  at  liberty  to  place  the 
signal  at  stop  any  time  if  desired,  even  if  the  lock  should  prevent 
the  release  of  the  lever.  This  is  accomplished  by  the  employment 
of  a  half  reverse  lock. 

On  mechanical  signals  where  circuit  controllers  are  needed  for 
the  control  of  the  indication  circuit  these  must  be  attached  so  that 
they  are  operated  by  the  semaphore  arm  and  not  by  the  up  and 
down  rod. 

The  Proper  Placing  of  the  Indication  Lock.  The  distant 
indication  lock  is  almost  invariably  placed  on  the  home  signal 
lever  on  account  of  the  mechanical  locking  existing  between  them, 
except  at  places  where  the  home  signal  itself  is  a  power  operated 
signal.  In  such  a  case  an  indication  lock  is  desirable  for  both 
signals.  Special  mechanical  locking  must  then  be  provided  be- 
tween the  levers  which  will  permit  the  placing  of  the  home  and 
the  distant  signal  levers  at  their  normal  latching  position,  should 
a  failure  of  the  indication  lock  prevent  the  distant  lever  from 
being  released. 

Dynamic  Indication.  With  the  dynamic  indication  scheme, 
the  indication  is  not  given  by  current  drawn  from  the  main  source 
of  supply  which  operates  the  signal,  but  the  indication  current  is 
procured  by  power  produced  at  the  signal  caused  by  the  back- 
ward rotation  of  the  motor,  which  is  effected  through  the  release 
of  a  holding  circuit  when  the  controlling  lever  has  been  placed 
normal  and  after  the  signal  is  indicating  stop. 

Fig.  57  illustrates  the  principles  of  the  dynamic  indication 
scheme  as  employed  for  low  voltage  signals  and  in  which  the 
power  for  the  energization  of  the  indication  magnet  is  developed 
at  the  signal.  The  current  is  generated  by  the  backward  rotation 
of  the  motor,  and  flows  to  the  indication  magnet,  as  shown,  and 
back  to  the  signal  motor.  A  cross  at  "X"  will  shunt  the  indicat- 
ing magnet  and  prevent  an  indication. 

Electro-Mechanical  Interlocking.  In  electro-mechanical 
interlocking  (the  Post  System)  the  switches  are  manually  oper- 
ated by  a  mechanical  interlocking    lever    located    in    a    regular 

64 


INDICATION    LOCKING 

interlocking  frame,  and  electrically  controlled  by  an  electric  lever 
placed  above  the  former.  Each  mechanical  switch  throwing  lever 
has  a  mechanical  lock  between  it  and  its  electric  controlling  lever, 
the  locking  being  so  arranged  that  the  controlling  lever  must  be 
thrown  to  its  middle  position,  thereby  effecting  the  unlocking  of 
the  mechanical  switch  throwing  lever,  which  can  then  be  operated. 
After  the  switch  lever  has  been  thrown  and  latched,  and  after 
the  switch  is  in  a  corresponding  position  and  locked,  then  only 
can  the  stroke  of  the  electric  lever  be  completed,  which  in  turn 
locks  the  mechanical  lever. 

A  circuit  for  a  switch  movement  is  shown  in  Fig.  58.  and  the 
-witch  lever  partly  reversed  will    unlock    the    switch    throwing 


Electric 
lever 


Ind  mag. 


-Lever  roller 

Contacts  on  roller. 


FIG.   58. 


lexer  by  the  withdrawal  of  lock  rod  "C,"  which  rested  in  a  notch 
in  the  horizontal  rod  "1)."  The  reversal  of  mechanical  lever  "E" 
will  cause  the  reversal  of  the  switch,  which  again  will  cause  the 
closing  of  contact  "F,"  thereby  completing  the  reverse  indication 
circuit.  Current  will  flow  through  contact  "F,"  wire  1,  contact 
on  electric  lever,  wire  2  and  indication  magnet  to  battery  nega- 
tive. This  will  permit  the  full  reversal  of  the  electric  lever  which, 
through  the  lock  rod  "C,"  will  lock  the  mechanical  lever,  the  lock 
rod  then  entering  notch  "G."  The  same  operation  is  performed 
with  the  throwing  of  the  switch  normal,  when  contact  "II"  at  the 
switch  will  close  the  normal  indication  circuit. 

65 


ELECTRIC    LOCK  IXC 

Polarized  Switch  Indication.  On  railroads  where  only  the 
most  up-to-date  developments  in  signal  devices  and  schemes  are 
installed  the  check  oh  the  position  of  a  switch,  as  obtained  with 
the  use  of  F.  P.  L.  (see  electric  bolt  lock  in  Chapter  V),  is  not 
considered  sufficient.  Hence  schemes  have  been  devised  whereby 
an  electric  indication  of  the  position  of  the  switch  is  secured  which 
will  give  a  positive  indication  that  a  switch  has  responded  to  the 
lever  movement:  The  reliance  formerly  placed  upon  the  lever- 
man's  judgment  as  to  the  integrity  of  the  mechanical  connection  is 
therefore  made  unnecessary.  The  most  reliable  and  adequate 
scheme  devised  for  this  protection  is  that  obtained  with  what  is 
generally  known  as  the  "SS"  relay,  which  is  controlled  through 
the  "SS"  or  the  polarized  indication  circuit. 

"SS"  Circuit.  The  "SS"  circuit  was  originally  used  in  con- 
nection with  electro-pneumatic  interlocking,  but  its  features,  as 
applied  in  present  day  interlocking  practice,  have  been  changed. 
In  "SS"  circuits  the  position  of  each  switch  is  repeated  in  the 
interlocking  tower  by  the  use  of  a  polarized  relay.  This  relay 
should  preferably  be  a  specially  designed  relay  of  the  three-posi- 
tion motor  type,  which,  besides  having  a  normal  and  reverse 
position,  has  the  moving  armature  or  member  counterweighted 
so  as  to  return  to  a  center  or  neutral  position  with  all  contacts 
open,  when  all  current  is  cut  off  from  its  control.  The  switch 
circuit  controller  used  for  the  control  of  "SS"  relays  should  pre- 
ferably have  a  special  cam  arrangement,  designed  and  adjusted 
to  force  the  adjustment  of  the  switch  circuit  controller.  The 
switch  circuit  controller  should  also  require  an  adjustment  of 
34  inch  or  less ;  in  other  words,  the  switch  circuit  controller 
should  necessitate  an  adjustment  to  secure  the  opening  of  the 
"SS"  circuit  when  the  switch  points  have  moved  not  over  %. 
inch  from  the  stock  rail  in  either  position  and  hold  the  contacts 
opened  until  the  switch  points  have  closed  to  within  %  inch  of 
the  opposite  position.  Such  adjustment  of  these  switch  circuit 
controllers,  while  not  specially  required  for  the  control  of  the 
three-position  "SS"  relays,  will  be  found  very  desirable,  as  it 
precludes  the  possibility  of  any  wrong  adjustment  of  the  switch. 

Fig.  59  shows  the  "SS"  circuit  arrangement  for  a  single  switch, 
"E"  being  the  relay  and  "F"  the  switch  circuit  controller.     The 

66 


INDICA 770  A'    LOCKING 


key  to  the  circuit  controller  adjustment  is  shown  in  sketch  "A," 
indicating  at  what  points  each  contact  should  make  and  break- 
through a  complete  cycle  of  a  switch  operation  at  places  where  a 
}i  inch  switch  point  adjustment  is  standard.  It  will  be  noted 
that  the  polarized  character  of  the  circuit  is  obtained  by  the  cir- 
cuit controller  acting  as  a  polechanger,  which  inverses  the  current 


z 

ui 
Cr 

J 

i 
£ 

c 

o 

0 

u. 

o 
Ik 

UI 

ft 

IT 

r 

X 

> 

O 

r 

.♦ 

JT 

U) 

or 

aU 

■ 

1 
1 

—  A 

o 

i 

— IC 

DH 


FIG.   59. 


a-    i      1  -iB 

fA) 


through  the  "SS"  relay.  These  contacts  are  also  arranged  so 
that,  when  the  switch  is  in  transit  or  is  not  fully  locked  at  normal 
and  reverse,  the  two  wires  leading-  to  the  "SS"  relay  in  the  tower 
will  be  short  circuited  or  placed  on  a  closed  circuit  by  means  of 
wire  "G,"  and  the  relay  will  therefore  not  only  be  de-energized, 
but  will  be  absolutely  short-circuited.  The  protection  against 
crosses  and  false  indication,  secured  not  only  by  this  short  cir- 
cuiting feature,  but  by  the  polarized  character  of  this  scheme  of 
indication  and  its  entire  isolation  from  all  other  circuits  or  com- 
mons, will  be  evident. 


-V.V 


<C1J: 


FIG.  60. 


Fig.  60  shows  bow  the  control  and  cross-protection  of  an  "SS" 

circuit  for  a  cross-over  can  be  accomplished  by  means  of  only 
one  "SS"  relay  and  a  minimum  number  of  wires  between  the  two 
switches.  An  indication  lock  placed  on  the  switch  lever  and  its 
circuit  so  arranged  that  only  with  the  lever  in  the  normal  indicat- 
ing position  and  the  "SS"  relay  repeating  the  normal  position  of 

67 


ELECTRIC    LOCKING 

the  sw  itch  can  the  lever  lock  he  energized,  will  give  a  reliable  indi- 
cation that  the  switch  is  in  the  position  corresponding  with  that  of 
the  lever.  The  same,  of  course,  is  true  with  regard  to  the  reversal 
of  a  switch  and  the  circuit  Fig.  61  shows  the  circuit  arrange- 
ment. The  "SS"  relays  can  he  used  to  advantage  by  accomplish- 
ing, within  the  interlocking  tower,  the  selecting  for  all  the  signals. 
This  is  called  the  "SS"  control  of  signals  and  the  control  for  all 
is  taken  through  the  "SS"  relays,  as  may  he  required,  for  every 
possible  route  for  any  given  signal. 

Switch  Indication  on  F.  P.  L.  Lever.  .Switch  indication 
can  also  be  procured  by  placing  the  lock  on  the  F.  P.  L.  lever  for 
the  switch  which  it  locks.     The  lever  lock  on  the  F.  P.  L.  lever 


FRU.4 


3 


OSS  R61AY  , 

for  sw  3  I       iss  reiay 

°T     -        ,  R+     |  I     FORSW.'i 

3  R 


¥ 

& 


%\ 


FIG.  61.  FIG.  62. 


must  be  a  normal  lock,  which  is  controlled  in  the  same  manner 
as  the  switch  indication  lock.  This  scheme,  shown  in  Fig.  62, 
will  prevent  the  reversal  of  the  F.  P.  L.  lever  and  the  consequent 
release  of  the  signal  lever  unless  the  position  of  the  switch  and 
the  switch  lever  correspond.  If,  instead  of  the  employment  of 
a  floor  push,  a  lever  circuit  controller  contact  on  the  F.  P.  L. 
lever  is  desired,  the  lever  lock  can  be  made  a  half  normal  lock 
so  that  a  wider  adjustment  of  the  contact  can  be  maintained. 

Electric  Interlock engs.  Various  sytems  for  the  control  of 
units  at  an  interlocking  by  power  have  been  developed  and  there 
are  at  present  in  practical  use  seven  different  systems  of  electric 
interlockings,  representing  the  production  of  five  principal  com- 
panies, and  each  one  designed  to  meet  the  exact  requirements  of 
up-to-date  signaling  and  each  one  possessing  distinctive  features 

68 


IXDICATIOX    LOCKING 

in  their  mechanical  and  electrical  design  and  in  their  indication 
methods. 

American  Electric  Interlocking.  In  this  system,  an  in- 
duced current  for  indication  is  taken  from  the  main  operating 
source  but  stepped  up  by  an  induction  coil  located  at  the  function. 
Fig-.  63  shows  the  principles  of  indication  in  a  switch  movement, 
only  such  wires  as  are  used  in  the  indication  being  shown.  "A" 
represents  the  lever  contacts  operated  through  a  straight  pull  of 
the  lever  and  "B"  the  contacts  operated  by  a  twisting  movement 
of  the  lever,  "C"  the  controller  contacts  at  the  switch,  operated 
in  unison  with  the  lock  bar  "T,"  and  "D"  the  polechanger  move- 
ments controlled  by  the  normal  pole  magnet  "N,"  and  reverse 
pole  magnet  "R."  When  a  switch  is  thrown  from  the  reverse 
to  the  normal  position,  contacts  "A"  will  be  in  the  position  shown 
and  "F"  and  "G"  will  be  made.  Current  will  then  flow  through 
the  primary  "P"  of  the  induction  coil  "W,"  creating  a  current  of 
from  300  to  5,000  volts  in  the  secondary,  which  passes  to  the 
spark  gap  "G,"  on  the  interlocking  machine,  and  to  common 
through  the  indication  relay  "I,"  thereby  making  contacts  "H." 


FIG.  63. 


FIG.   64.       FTG.    65. 


Current  will  then  flow  through  the  normal  indication  magnet  and 
stroke  completer  "N,"  energizing  the  indication  magnet,  releas- 
ing the  final  movement  of  the  lever,  and  also  completing  this 
movement  through  the  stroke  completer.  This  movement  breaks 
contacts  "F"  and  "G."  An  indication  cannot  be  received  while 
coil  *'S"  (the  safety  magnet,  energized  while  the  function  is  oper- 
ated) is  taking  current,  for  the  reason  that  it  will  prevent  coil 
"I"  from  attracting  the  armature.  Positive  battery  introduced 
into  the  indication  wire  cannot  possibly  produce  a  false  indication 

69 


ELECTRIC    LOCKING 

since  the  current,  in  order  to  jump  across  the  spark  gap,  must 
of  necessity  be  of  a  higher  voltage  than  that  used  in  the  operation 
of  the  system,  or  by  any  power  plant,  street  railway  or  lighting 
system. 

Fig.  64  shows  the  indication  and  stroke  completing  devices 
applied  to  a  switch  lever  in  the  normal  position.  The  top  coil  is 
the  reverse  and  the  bottom  coil  the  normal  indication  and  stroke 
completer  coil.  A  small  coil  acts  as  an  indication  magnet  by 
attracting  the  armature  "A,"  and  a  large  coil  acts  as  a  stroke 
completer  by  attracting  the  vertical  plunger  "B."  The  plunger 
is  attracted  upward  for  a  reverse  lever  movement  and  downward 
for  a  normal  movement.  Fig.  65  shows  the  lever  held  in  the  re- 
verse indication  position.  The  lever  has  received  the  indication 
and,  with  the  indication  latch  "C"  in  this  position,  is  free  to  be 
moved  from  the  vertical  to  the  oblique  position  through  the  lift- 
ing of  "B"  by  the  stroke  completer  coil.  It  will  be  noted  that 
the  lever  when  in  its  normal  or  reverse  indication  position  is  held 
by  the  normal  and  reverse  indication  latches  "C"  and  "E"  en- 
gaging the  dog  "D,"  which  prevents  any  manipulation  of  the 
lever  to  the  right  or  left. 

Federal  Electric  Interlocking.  In  this  system  the  current 
for  the  indication  is  taken  from  the  operating  battery  source,  but 
is  supplied  to  the  indication  magnet  in  such  a  manner  as  to  insure 

/v. 


Indication. 


FIG.  66. 


absolute  safety  in  indication.  Fig.  66  shows  the  principles  used 
in  this  system  to  prevent  a  false  or  premature  indication.  "F" 
represents  the  lever  contacts  and  "G"  the  controller  contacts  at 
the  switch  actuated  by  bar  "H,"  which  works  in  unison  with  the 
lock  bar.  Safety  magnet  "S"  and  indication  magnet  "I"  will 
lock  the  lever,  should  current  flow  through  either  one  while  the 

70 


IX  DIC  ATI  OX    LOCKING 

lever  is  not  being  manipulated.     "E"  is  a  balanced  cross-protec- 
tion magnet  comprising  a  circuit  breaker  held  normally  closed 
while  no  current    is    flowing    through    the    coils  "D"  and  "C." 
These  coils  are  of  equal  resistance  and  wound  in  opposite  direc- 
tions, so  that  when  an  equal  amount  of  current  flows  through 
both  coils  simultaneously  they  will  neutralize    each    other;    but 
should  current  flow  through  either  coil  alone,  the  armature  will 
be-attracted  and  this  will  release  the  main  circuit  breaker,  which 
is  controlled  through  the  contact.     The  safety  relay  "Z"  has  two 
solenoids,  "A"  and  "B,"  and  plungers   wheih  are  so  inter-con- 
nected that  the  operations  of  one  plunger  will  also  affect  the  other. 
Assume  the  switch  to  be  reversed  and  the  lever  to  be  returned 
to  the  position  shown.     The  indicating  current  will  flow  through 
magnets  "A,"  "D"  and  "S,"  contact  on  the  lever  "F,"  contact  on 
indicator  selector  "T"  (closed  only  when  the  switch  is  full  normal 
or  full  reversed  and  locked  in  position)  indication  wire,  contact 
"U,"  indication  magnet  "I,"  and  magnets  "B"  and  "C."     In  the 
meantime  the  motor  has  stopped  on  the  snubbing  circuit,  and  a 
current  will  then  flow  from  the  motor  armature  through  magnet 
"B,"   lever  contact,   contact  on   "G"  and  reverse  field   winding. 
This  would  take  place  immediately  after  the  running  current  of 
the  motor  was  cut  off  and  would  bring  the  motor  to  a  dead  stop, 
and  this  current  flowing  though  magnet  "B"  would  return  the 
magnet  to  its  normal  position,  thereby  again  closing  contact  "M," 
when  the  final  release  of  the  lever  might  be  accepted,  the  indica- 
tion magnet  having  been  released.    In  order  to  receive  an  indica- 
tion, several  conditions  must  exist  simultaneously  and  within  a 
certain  time.    The  indication  selector  "T"  must  be  in  the  position 
corresponding  with  the  position  of  the  lever.     Contact  "U"  must 
be  closed  by  current  flowing  through  magnet  "A."     This   will 
make  it  possible  to  place  the  lever  normal,  but  the  placing  of  the 
lever  normal  will  break  a  lever  contact,  which  is  connected  in 
multiple  with  contact  "M,"  keeping  the  main  circuit  breaker  on 
the  operating  board  closed.     Therefore,  it  is  necessary  that  the 
dynamic  current  generated  through  the  momentum  of  the  motor 
energize  coil  "B,"  thereby  making  contact  "M."  Should  this  fail, 
the  operating  current  will  be  cut  off.     A  cross  between  "\"  and 
the  indication  wire  can  cause  a  premature  indication  so  far  as 
the  completion  of  the  lever  movement  is  concerned,  but  this  would 
not  close  "M,"  and  would  consequently  open  the  cut-ont. 

71 


ELECTRIC    LOCKING 

The  only  remaining  chance  for  a  false  indication,  which  might 
be  caused  by  a  positive  cross,  introduced  through  a  live  wire  from 
some  other  function,  is  prevented  as  follows :  While  the  lever  is 
in  the  reverse  position,  as  indicated  in  dotted  lines  on  lever  con- 
tacts "F,"  the  contacts  on  safety  relay  "Z"  are  in  the  opposite 
position;  that  is,  contacts  "U"  are  open  and  contacts  "M"  closed. 
The  switch  in  a  corresponding  position  will  have  the  reverse  con- 
tact on  indication  selector  "T"  closed.  Hence  the  indication  wire 
with  the  lever  and  switch  in  the  reverse  position  will  be  con- 
nected with  positive  battery  through  magnets  "S,"  "D"  and  "A" 
in  series.  As  soon  as  the  lever  is  placed  normal,  preparatory  to 
a  normal  switch  movement,  the  lever  contacts  will  be  closed,  as 
shown  in  Fig.  66.  This  will  immediately  connect  the  indication 
wire  with  battery  negative,  through  reverse  contact  on  "T,"  wire 
"R,"  contact  "F,"  and  magnets  "B"  and  "C."     This  is  the  path 


FIG.  67. 


which  any  positive  battery  from  other  functions  introduced 
through  a  cross  with  the  indication  wire  will  take  and  thereby 
effect  the  opening  of  the  main  circuit  breaker  (it  will  be  noted 
that  the  introduced  current  in  this  case  flows  through  coil  "C" 
only)  before  the  switch  movement  will  have  an  opportunity  to 
respond  to  the  movement  of  the  lever. 

Fig.  67  illustrates  the  lever  and  indication  parts  of  the  inter- 
locking machine  in  the  normal  position.  The  lock  slide  "L" 
carries  two  square  dogs,  "A"  and  "B,"  which  are  free  to  move 
vertically  but  held  in  their  raised  position  by  the  flat  springs  "C," 
through  the  medium  of  retaining  balls.  The  locking  is  effected 
by  the  magnet  heads  "G"  and  "H"  engaging  with  the  pins  "D," 
"E"  and  "F"  on  the  side  of  the  lock  slide.  The  reversal  of  the 
lever  will  move  the  lock  slide  "L"  in  the  direction  of  the  arrow, 
provided  safety  magnet  head  "H"  is  down  so  it  will  pass  by  pin 

12 


INDICATION    LOCKING 

"D,"  when  dog-  "A"  will  strike  plate  "J"  and  dog  "B"  plate  "K," 
thereby  forcing  the  dogs  to  their  lower  position.  The  dogs  will 
remain  in  this  position  and  the  lock  slide  can  be  moved  until  the 
dogs  engage  it  with  the  raised  portion  of  the  magnet  guide  at 
"O"  and  "R,"  when  the  lever  is  stopped  until  the  indication  is 
received.     Fig.  68  shows  the  lever  in  the  indicating  position,  the 


FIG.  68. 


indication  received  and  the  dogs  raised.  When  the  dogs  are 
raised,  the  lever  can  be  placed  in  its  complete  reverse  or  normal 
position  at  any  time,  the  dogs  being  held  raised  through  retaining 
balls  and  springs  "C." 


fv  c  ?  ?  , 

-*-*\'tfri 

2§V 


FIG.  69. 

The  G.  R.  S.  Scheme  of  Indication.  The  distinguishing 
feature  of  the  G  R.  S.  system  is  the  dynamic  indication.  Dynamic 
indication  means  an  indication  procured  at  and  generated  by  the 
motor  which  operates 'the  function.  Fig.  69  shows  a  switch  cir- 
cuit with  only  enough  of  the  circuits  to  illustrate  the  principles 
of  the  indicating  scheme  and  the  means  employed  to  prevent  a 

73 


ELECTRIC   LOCKING 

premature  indication.  "A"  is  the  lever  contacts  and  **B"  the 
polechanger,  which  is  operated  automatically  by  the  lock  plunger 
in  the  final  part  of  the  movement  of  the  switch  and  during  all 
intervening  time  under  control  of  the  lever  by  means  of  the  pole- 
changing  magnets  "R"  and  "X."  "E"  is  the  switch  motor  arma- 
ture and  "F"  the  field.  Assume  the  switch  and  the  lever  as  being 
moved  from  the  reverse  to  the  normal  position.  The  switch  hav- 
ing completed  its  movement  normal  will  switch  the  contacts  on 
the  polechanger  "B,"  as  shown,  with  the  result  that  the  operating 
current  is  cut  off  the  motor  circuit.  This  will  also  close  a  circuit 
through  which  the  momentary  current  generated  by  the  motor 
acting  as  a  generator  through  the  momentum  acquired  will  reach 
the  indication  magnet.  This  also  acts  as  a  snubbing  circuit  for 
the  motor.  It  is  obvious  that  the  only  effect  that  a  cross  between 
wire  "R"  and  common,  as  at  "X,"  could  have  would  be  to  pre- 
vent current  reaching  the  indication  magnet.  If  a  cross  should 
occur  between  the  live  wire  "N"  and  the  wire  "R,"  as  at  "Y," 
the  current  thus  introduced  will  flow  in  the  direction  of  the 
arrows  through  the  indication  magnet  and  the  polarized  relay 
"G"  in  a  direction  opposite  to  the  regular  indicating  current  and 
cause  the  opening  of  contact  "H."  which  controls  the  main  circuit 
breaker.  Polarized  relay  "G"  is  so  constructed  that  when  cur- 
rent flows  in  a  given  direction  through  it,  it  causes  the  contact 
"H"  to  open,  which  in  turn  opens  the  main  cut-out  and  interrupts 
the  flow  of  current  through  the  polarized  relay  as  well  as  all 
circuits  connected  with  that  cut-out.  The  current  introduced 
through  a  cross  at  "Y"  could  not  possibly  energize  the  indication 
magnet  even  for  a  moment,  as  this  current  would  pass  through 
the  safety  magnet  "S,"  which  would  hold  the  indication  arma- 
ture "L." 

To  remove  the  only  remaining  chance  for  a  false  indication, 
selector  "C"  is  connected  in  the  operating  circuit.  It  comprises 
two  magnets,  one  in  each  operating  circuit.  The  lever  "M"  and 
the  contacts  "P"  and  "Q"  form  a  circuit  switch,  the  function  of 
which  is  to  close  the  proper  indication  circuit.  If  the  operating 
circuit  happens  to  be  open  and  another  switch  attempts  to  indi- 
cate through  the  wrong  lever  ( assuming  two  switches  being 
operated  simultaneously),  the  corresponding  indication  circuit 
will  not  be  closed,  so  it  would  be  impossible  for  such  currents  to 
reach  the  indication  magnet.     Should  the  operating  circuit  be  in 

74 


INDICATION    LOCKING 


good  order  and  another  function  indicate  through  the  wrong 
lever,  the  indication  selector  will  be  in  a  corresponding  position, 
but  the  magnet  "S"  will  be  energized,  as  the  switch  will  take 
current  until  the  movement  is  completed.  The  object  of  the  indi- 
cation selector  is  also  to  eliminate  any  chance  for  a  premature 
indication  should  the  switch  points  happen  to  be  blocked  so  as. 
not  to  complete  their  stroke,  which  condition  might  cause  the 
motor  to  revolve  backward,  due  to  the  opening  of  the  points,  thus 
producing  a  dynamic  current  which  might  have  a  tendency  to 
cause  an  indication  if  the  lever  is  restored  to  the  position  from 
which  it  started  at  that  particular  moment.  It  will  be  evident 
that  this  also  is  effectively  prevented. 

Fig.  70  shows  a  switch  lever  in  its  normal  position.  When  the 
lever  is  moved  from  full  normal,  the  projection  "M"  on  lever 
"D,"  coming  in  contact  with  projection  "K"  on  latch  "L,"  causes 
the  latch  to  assume  the  position  shown  in  Fig.  71,  thus  bringing 


FIG.  71. 


FIG.  70. 


projection  "J"  into  the  path  of  the  tooth  "Q."  In  further  re- 
versing the  lever,  the  tooth  "Q"  comes  in  contact  with  a  similar 
projection  on  the  cam  "N"  and  causes  it  to  revolve  into  the  hori- 
zontal position  (shown  dotted  in  Fig.  71),  thus  forcing  dog  "P" 
under  and  locking  "L"  in  its  horizontal  position.  In  moving  to 
the  reverse  indication  position,  the  cam  "N"  is  revolved  into  the 
position  shown  by  full  lines  (Fig.  71)  and  the  lever  is  stopped  at 
projection  "J,"  further  movement  being  prevented  until  the  indi- 
cation current  is  received.  The  indication  current  flowing 
through    magnet    "I,"    thereby    lifting    armature    "T,"    causes 

75 


ELECTRIC    LOCKING 

plunger  "R"  to  strike  dog  "P"  and  throw  it  out  from  under  latch 
"L."  The  latch  being  thus  released  will  resume  the  position 
shown  in  Fig.  70  and  permit  completing  the  stroke  of  the  lever. 
The  stroke  from  normal  to  reverse  is  accomplished  in  the  same 
way. 

The  Hall  Scheme  of  Indication.  In  this  system  an  alter- 
nating current  of  110  volts  flows  from  the  tower  to  the  function, 
where  it  is  stepped  up  by  a  transformer  to  330  volts  of  commer- 
cial frequency,  and  the  alternating  current  thus  emanating  from 
the  function  is  used  for  the  indication.     Fig.  72  shows  in  a  sim- 


D 


B 


E 


r-cs> 


N 


(Common 


{Primary 


FIG.   72. 


plitied  diagram  the  principles  of  the  indication  scheme  with  all 
wires,  contacts  and  apparatus  not  directly  involved  eliminated. 
"A"  represents  the  lever  contacts  and  "B"  the  controller  con- 
tacts, actuated  by  "C,"  which  works  in  unison  with  the  lock  bar. 
"D"  is  the  indication -selector  comprising  four  coils,  the  two  in- 
side of  which  are  connected  in  multiple  with  the  normal  and 
reverse  operating  wires  respectively,  and  the  two  outside  coils 
being  controlled  by  the  motor  snubbing  circuit  after  the  comple- 
tion of  the  switch  movement.  Magnet  "S"  (safety  lock  magnet) 
performs  two  functions,  one  of  which  is  to  lock  the  lever  in  the 
full  normal,  full  reverse  and  operating  positions,  with  the  safety 
coil  energized ;  and  the  other  function  is  to  unlock  the  lever  when 
it  has  reached  the  indication  position  by  its  being  de-energized. 
It  has  two  windings,  one  of  low  ("L")  and  the  other  of  high 
("H")  resistance.  The  high  winding  is  connected  in  parallel 
with  a  fuse,  which  makes  the  safety  magnet  effective  with  or 
without  the  fuse  in  the  circuit.  The  indication  magnet  ("I")  is 
immune  to  direct  current  or  to  alternating  current  of  250  volts 

76 


IX  DIC  ATI  OX    LOCKING 

or  less.  It  will  therefore  be  evident  that  the  alternating  primary 
current  from  the  tower  (110  volts)  will  under  no  circumstances 
directly  operate  the  indication  magnet.  Assume  the  switch  re- 
versed and  being  moved  to  the  normal  position,  as  shown  in  the 
figure.  With  the  placing  of  the  lever  normal,  positive  battery 
flowing  over  "N"  wire  will  cause  the  contacts  "K,"  "L,"  "M" 
and  "O"  to  make.  As  soon  as  the  switch  has  completed  its  move- 
ment, controller  "B"  will  be  in  the  position  shown,  thereby  break- 
ing the  normal  control  circuit.  This  will  de-energize  magnet 
"N"  of  the  indication  selector  "D,"  which  in  turn  would  break 
contacts  "K,"  "L,"  "M"  and  "O,"  thereby  preventing  an  indica- 
tion. The  momentum  of  the  motor,  however,  which  with  the 
completion  of  the  movement  is  placed  on  a  closed  circuit,  will 
generate  a  current  which  will  flow  through  contacts  "K"  and 
"W,"  field  coils  "T,"  magnet  "N,"  contacts  "V"  and  "L"  to  arma- 
ture "F."  This  current,  which  also  acts  as  a  snubbing  circuit 
preventing  undue  jar  to  the  movement,  will  energize  magnet  "X" 
and  maintain  the  indication  circuit  closed  for  a  predetermined 
interval  at  the  selector.  The  %-\on.  motor  generator  "J"  (or  an 
a.  c.  supply  from  a  commercial  source),  located  in  the  tower 
whose  circuit  has  been  completed  through  a  contactor  closed  with 
the  manipulation  of  the  lever,  will  cause  alternating  current  to 
flow  over  primary  wire  contacts  "U"  and  "M,"  primary  coil  "P" 
of  transformer  "G,"  back  to  generator.  The  current  thus  induced 
in  the  secondary  coil  "S"  of  transformer  "P"  will  flow  through 
contact  "O,"  on  controller  "D,"  contact  "W"  on  controller  "B," 
lever  contact'  "H"  and  indication  magnet  back  to  the  transformer. 
This  will  permit  the  completion  of  the  lever  movement.  In  the 
meantime,  the  switch  motor  having  come  to  a  rest,  contacts  "K," 
"L,"  "M"  and  "O"  will  break.  It  is  to  be  noted  that  no  cross 
between  the  "R"  and  "N"  wires,  as  at  "X,"  can  cause  a  false 
indication,  because  the  indication  magnet  would  be  immune  to  a 
direct  current ;  that  a  cross  at  "Y"  would  prevent  an  indication ; 
also  that  the  indication  current  emanates  from  the  function  and 
is  not  existent  prior  to  the  movement  of  the  function  and  cannot 
be  procured  through  a  single  break  in  either  indication  wire,  but 
being  an  induced  current  must  flow  back  to  the  function  from 
which  it  was  produced.  Furthermore,  in  order  to  obtain  an  indi- 
cation several  conditions  must  simultaneously  obtain  before  the 
stepped-up  current  or  indication  current  can  reach  the  indication 

77 


ELECTRIC   LOCKING 

magnet.  Safety  magnet  "S"  must  have  taken  current;  the  lever 
must  be  in  the  indication  position;  controller  contacts  "B"  must 
be  in  position  corresponding  with  the  position  of  the  lever,  and 
the  current  generated  by  the  momentum  of  the  motor  must  hold 
closed  the  indication  contacts.  The  indication  magnet,  being 
immune  to  direct-current  or  alternating  current  of  250  volts  and 
less,  cannot  possibly  be  energized  by  a  cross  from  either  operat- 
ing or  primary  current. 

Fig.  73  shows  a  cut  sectional  view  of  a  switch  lever.  As  a 
means  of  preventing  the  movement  of  a  switch  lever  to  full  re- 
verse or  full  normal  position  before  a  proper  indication  is  re- 
ceived, two  mechanical  locking  dogs,  "C"  and  "D,"  are  arranged 
in  each  lever  slide.  These  dogs  are  mechanically  forced  down  by 
the  lugs  "F"  and  "J"  into  a  slot  in  the  bed-plate  on  which  the 
lever  slide  "P"  rests,  and  can  only  be  forced  out  of  the  slot  by 


FIG.  73. 


FIG.  74. 


the  action  of  the  indication  magnet  "I."  which  will  cause  the  rais- 
ing of  indication  release  "B,"  and  by  the  action  of  safety  magnet 
"S,"  which  will  cause  the  raising  of  plunger  "G"  and  armature 
plate  **L."  When  the  lever  reaches  the  indicating  position,  as 
shown  in  Fig.  74,  and  while  the  function  is  taking  current,  safety 
magnet  "S,"  connected  in  series  with  the  operating  circuit,  will 
take  current  and  consequently  cause  the  raising  of  dog  "D," 
which  is  afterward  held  by  retaining  ball  "O."  After  the  com- 
pletion of  the  movement  of  the  function  the  indication,  being 
received,  will  produce  an  alternating  current  through  the  indi- 
cation coil  "I,"  which  repels  the  copper  ring  "A."  which  again 
operates  release  "B"  and  places  it  in  the  position  shown.  This 
raises  the  indication  dog  "C"  out  of  the  recess  and  it  is  held  in 
position  by  the  retaining  spring  "X"  and  the  ball  "O."    The  lever 

78 


IND1 CA TIOX    LOCK IN G 

movement  can  be  completed  afterward.  Should  two  levers  be 
manipulated  simultaneously,  one  cannot  indicate  through  the 
other,  as  the  indication  coils  are  in  series  with  their  respective 
transformer  secondaries,  and  the  movement  of  the  lever  for  the 
function  that  is  not  taking"  current  cannot  be  completed  because 
the  "S"  magnet  will  be  de-energized.  To  accomplish  the  locking 
of  the  lever  in  the  full  normal  and  reverse  and  operating  posi- 
tions with  the  safety  coil  energized,  two  horizontal  lugs,  "H"'  and 
"K,"  are  attached  to  each  lever  slide.  The  armature  of  the  safety 
magnet  has  two  vertical  lugs  projecting  up  from  the  face  of  the 
armature  plate  "L,"  which  engage  the  horizontal  lugs,  "H"  and 
"K."  Thus,  if  the  safety  coil  is  taking  current  before  the  lever 
is  manipulated  or  after  the  indication  is  received,  the  lever  is 
locked  in  these  positions.  It  will  be  obvious  that  in  order  to  make 
a  complete  lever  movement  the  safety  magnet  must  first  be  ener- 
gized and  then  de-energized,  in  addition  to  the  energization  of 
the  a.  c.  indication  magnet. 

The  Union  A.  C.  Indication.  In  this  system  the  indicating 
current  is  drawn  directly  from  the  main  battery,  but  it  is  trans- 
formed into  an  alternating  current.  A  convenient  means  for 
producing  the  current  used  for  indication  is  afforded  by  a  collec- 
tor ring  on  the  armature  shaft  of  the  switch  operating  motor 
connected  to  one  segment  of  the  commutator.  At  the  end  of  the 
switch  movement,  after  the  motor  has  been  disengaged  from  the 
mechanism  by  the  clutch,  the  operating  wire  is  switched  from  the 
operating  brush  to  the  brush  bearing  on  the  collector  ring.     The 


FIG.  75. 


FIG.   76. 


FIG.   77. 


motor  armature  will  continue  to  rotate  and,  as  the  segment  to 
which  the  ring  is  connected  alternately  approaches  and  then  re- 
cedes from  the  brush,  the  current  in  the  circuit  including  the 
primary  coil  of  the  transformer  will  in  turn  generate  an  alter- 

79 


ELECTRIC   LOCK  IXC 

nating  current  in  the  secondary  coil.  The  current  from  the  sec- 
ondary flows  through  the  coils  of  the  induction  motor,  causing 
a  rapid  rotation  of  the  armature,  which  results  in  lifting  the  indi- 
cation latch.  In  Fig.  75  the  indication  scheme  is  illustrated  in  a 
simplified  manner,  assuming  the  lever  being  placed  normal  and 
receiving  the  indication. 

It  can  easily  be  seen  that  a  connection  either  accidental  or  in- 
tentional of  the  wire  "N"  with  any  other  wire  would  cause  only 
a  direct  current  to  flow  through  the  primary  coil  of  the  trans- 
former, which  would  have  no  effect  on  the  secondary.  As  the 
induction  'motor  is  built  to  require  approximately  100  alterations 
per  second  to  make  it  operative,  it  is  quite  apparent  that  it  could 
not  be  affected  by  any  succession  of  impulses  that  could  be  pro- 
duced by  accident.  The  accidental  contact  of  "N"  wire  with  the 
wire  to  any  other  switch  which  is  in  the  act  of  indicating  could 
not  result  in  a  false  indication  because  it  is  in  connection  with 
the  operating  brush  of  the  motor  until  the  movement  is  com- 
pleted, which  would  hold  it  at  a  uniform  potential  either  high  or 
low,  and  would  prevent  fluctuation. 

Fig.  76  shows  the  indication  segment  "A"  for  a  switch  lever 
with  the  lever  in  its  normal  position.  "B"  is  the  indication  latch 
and  "M"  the  induction  motor.  The  turning  of  the  lever  will 
move  the  segment  "A"  in  the  direction  of  the  arrow,  thereby 
dropping  the  indication  latch  "B"  into  recess  "C."  Should  the 
latch  remain  up  it  would  strike  dog  "D,"  which  would  prevent 
the  reversal  of  the  lever  and  the  making  of  the  contacts  for  re- 
versal of  the  switch  movement.  The  lever  is  limited  in  its  move- 
ment by  the  indication  latch  striking  stop  "E."  Fig.  77  shows  the 
lever  in  the  indicating  position  and  the  indication  being  received. 
It  will  be  noted  that  the  indication  motor  "M"  has  its  armature 
shaft  in  a  vertical  position,  to  which  is  attached  a  piece  of  centri- 
fugal apparatus  similar  in  construction  to  the  governor  on  a 
steam  engine.  The  rapid  rotation  of  the  armature  will  separate 
the  weights  "N"  and  lift  the  indication  latch  and  release  the  lever. 

U.  S.  &  S.  Bi-Current  Indication.  In  this  system,  current 
is  caused  to  flow  towards  the  positive  pole  of  the  operating  bat- 
tery, while  at  the  same  time  the  operating  current  is  flowing  in 
other  parts  of  the  circuit.  Fig.  78  shows  the  indication  circuit 
for  a  switch  movement.     "A"  represents  the  lever  contacts  and 

80 


INDICATION    LOCKING 

"B"  the  indication  apparatus.  This  apparatus  comprises  a  polar- 
ized magnet  without  permanent  magnets,  however.  The  polari- 
zation is  effected  by  the  operating  current  passing  through  one 
of  the  magnet  coils  "K."  The  other  coil  "L"  must  then  have 
current  in  a  certain  direction  relative  to  the  driving  current  in 
order  to  actuate  the  latch  which  releases  the  lever.  To  cause 
current  to  flow  in  opposition  to  the  battery  is  the  purpose  of  the 


FIG.  7S. 


two  sets  of  coils  on  the  motor  armature  of  the  motor  operating 
each  function.  This  is  shown  at  "E,"  the  outside  set  of  brushes 
representing  the  operating  armature,  and  the  inner  set  repre- 
senting the  indication  armature.  "N"  and  "R"  are  the  normal 
and  reverse  motor  field  coils,  respectively.  When  the  motor  is 
driven  through  one  set  of  coils  on  the  armature,  the  counter  elec- 
tromotive force  of  this  set  is  nearly  equal  to  that  of  the  battery ; 
and  since  the  other  set  of  coils  is  rotating  at  the  same  speed  in  the 
same  magnetic  field,  its  counter  electromotive  force  is  the  same 
as  that  in  the  set  driving  the  motor.  The  result  is  that  a  poten- 
tial nearly  double  that  of  the  battery  is  produced  at  the  motor, 
so  that  current  can  be  readily  caused  to  flow  towards  the  positive 
pole  of  the  battery. 

It  will  be  assumed  that  the  lever  is  being  placed  normal  and 
that  the  switch  movement  is  just  completed.  Current  will  then 
flow  through  the  operating  brushes  of  armature  "E,"  keeping  the 
motor  running  idle  in  the  same  direction  as  the  last  movement  of 
the  switch.  The  current  for  the  energization  of  the  indication 
coil  "L"  will  ilow  from  the  indication  armature,  through  the 
magnet  coil  "L,"  and,  as  it  has  twice  the  voltage  of  the  operating- 
battery,  it  will  operate  the  indication  latch.  It  will  be  evident 
that  a  cross,  as  at  "X,"  could  not  cause  a  false  indication  because 
these  connections  would  have  the  full  positive  battery  voltage 
opposing  each  other.  A  ground  at  "Y"  would  have  the  same 
effect.  A  false  indication  could  not  result  from  the  wire  being 
crossed  with  the  indication  wire  to  another  switch  which  was  in 

81 


ELECTRIC    LOCKING 

the  act  of  indicating,  because  unless  the  switch  had  completed 
its  movement  and  a  change  in  circuits  been  made  at  the  motor, 
the  potential  would  be  held  down  by  the  motor  which  had  not 
reached  the  proper  point  for  indicating. 


Q 


FIG.  79. 


ca      £3; 


)     L 


3        C 


U         CT 


h  —       R 


3g 


° cr 


FIG.  80. 


Fig.  79  shows  the  indicating  part  of  a  switch  lever  in  the  full 
normal  position.  The  movement  of  the  lever  will  impart  move- 
ment to  bar  "I,"  and  thereby  force  the  indication  latch  "V"  into 
the  notch  "R,"  in  this  way  insuring  that  the  latch  is  performing- 
its  function  without  entirely  depending  upon  spring  "S."  Fig. 
80  shows  the  lever  in  its  reverse  indication  position.  Indication 
latch  "V,"  which  rested  in  notch  "R,"  is  lifted  by  the  indication 
magnet,  slot  "U"  permitting  this,  and  the  lever  "H"  is  ready  for 
its  final  movement.  The  indication  magnet  "G"  comprises  two 
energizing  coils,  "K"  and  "L."  The  coil  "K"  is  enclosed  within 
an  iron  tube  or  shell  which  forms  one  pole  of  a  magnet  energized 
by  coil  "L."  The  other  pole  of  the  magnet  resides  at  the  two 
ends  of  the  yoke  "M."  Within  the  coil  "K"  and  free  to  move  in 
a  vertical  direction  is  an  iron  core  having  a  Hat  iron  disc  attached 
to  each  end.  These  discs  are  the  poles  of  another  magnet  ener- 
gized by  the  coil  "K."  If  the  direction  of  the  current  in  the  coil 
"K"  is  such  as  to  make  the  upper  disc  a  north  pole  and  the  lower 
disc  a  south  pole  and  the  direction  of  the  current  in  the  coil  "L" 
is  such  as  to  make  the  shell  a  north  pole  and  the  ends  of  the  yoke 
south  poles,  the  movable  core  will  be  pushed  upward  :  but.  if 
the  current  in  either  coil  is  reversed  the  core  will  be  held  down. 

82 


IX DIC A TION    LOL  KING 


The  U.  S.  &  S  Type  "F"  Indication  System.  Indication  is 
procured  through  a  controller  at  the  switch  as  shown  in  big.  81, 
illustrating  the  principles  of  a  switch  indication  circuit.  Any 
voltage  may  he  employed  in  the  indication.  The  circuit  is  so 
arranged  at  the  switch  indication  circuit  controller  "L"  that. 
should  the  switch  remain  in  a  half-open  position,  the  indication 
circuit  proper  is  not  only  broken,  but  the  relay  "KR"  is  placed 
on  a  closed  circuit  through  wire  "M."  The  indication  is  procured 
through  the  indication  circuit  controller  "L,"  performing  the 
function  of  a  polechanger  switch,  which  causes  the  changing  of 
the  polarity  of  the  "KR"  relay  at  the  machine.  This  "KR" 
relay  is  typical  of  the  electro-pneumatic  and  the  type  "F"  electric 
system,  and  it  can  be  used  to  advantage  in  the  control  of  the  sig- 
nals by  selecting  the  control  circuit  through  the  relay  instead  of 

Y  k S± 

r  j=. — 


Fv 


*-z 


"L^V-a? 


*-0  0 


FIG.  81. 


FIG.  82. 


the  switch  boxes,  thereby  confining  the  complete  selection  cir- 
cuits to  the  tower.  It  will  lie  noted  that  a  complete  circuit  from 
the  switch  to  the  tower  and  back  again  must  be  maintained  in 
order  to  keep  the  "KR"  relay  energized  and  obtain  an  indication. 
A  cross  at  "X"  will  only  prevent  an  indication.  The  same  is  true 
in  regard  to  a  ground  at  "Y."  A  positive  cross  at  "Z"  will  reach 
common  through  the  indication  circuit  controller.  With  the 
relay  "KR"  in  the  position  shown,  the  circuit  is  made  for  the 
normal  indication  magnet  "N"  and  the  reversal  of  the  polarized 
armature  will  complete  the  circuit  for  the  reverse  indication  mag- 
net "R"  through  the  quick-acting  lever  contacts  "BO"  and 
"DQ."  Should  conditions  arise,  in  spite  of  all  precautions  de- 
scribed in  connection  with  the  indication  circuit,  tending  to 
produce  a  premature  indication,  it  will  presently  be  seen  that  the 
construction  of  the  indication  magnet  will  prevent  the  manipula- 
tion of  the  lever  so  affected. 

Fig.  82  shows  the  indication  segment  for  a  reverse  indication 
magnet.     "A"  shows  the  position  of  the  segment  with  the  lever 

83 


ELECTRIC    LOCKING 

in  the  full  normal  position.  The  lug  designated  as  "O"  on  the 
indication  segment  is  instrumental  in  protecting  the  system 
against  a  premature  indication.  It  will  he  plainly  seen  that 
should  the  indication  armature  "P"  he  held  up  for  any  reason, 
the  lower  locking  surface  of  the  latch  "Q"  would  then  engage 
with  lug  "O"  before  the  lever  had  moved  far  enough  to  close  the 
contacts  controlling  the  next  movement  of  the  switch,  thereby 
preventing  the  reversal  of  the  lever.  *'!'."  shows  the  indication 
segment  in  the  reverse  indicating  position  and  the  latch  is  shown 
energized,  which  will  allow  the  upper  locking  surface  of  the  latch 
to  clear  lug  "T"  for  the  final  release  of  the  lever.  The  normal 
indication  segment  is  of  a  similar  design. 

Electro-Pneumatic  System.  The  indication  is  provided  on 
the  battery  indication  principle  and  is  of  a  similar  design  as  the 
Union  Switch  &  Signal  Company's  style  "F"  previously  described. 

Adjuncts.  In  all  types  of  power  interlockings  employing 
various  methods  of  indicating  the  proper  response  of  a  function 
to  the  lever  movement,  it  is  desirable  to  apply,  in  addition  to 
these  schemes,  the  "SS"  circuit.  With  this  type  of  control  all  sig- 
nal selection  circuits  can  be  confined  to  the  tower,  so  that  during 
trouble  hunting  the  immediate  location  of  a  derangement  can  be 
accomplished  by  inspecting  the  "SS"  relays.  As  a  necessarv 
adjunct  to  indication  locking,  many  signal  departments  are  at 
present  equipping  the  semi-automatic  signal  levers  with  lights, 
the  control  of  which  being  so  arranged  that  they  will  burn  with 
the  signal  in  a  45  or  90-degree  position.  This  will  prevent  any 
delay  if  the  signal  is  not  cleared,  as  such  a  condition  can  readily 
be  discovered. 


84 


SECTION    LOCKING 

Definttion.  Section  locking  is  the  term  substituted  by  the 
Railway  Signal  Association  for  the  formerly  employed  nomencla- 
ture '^detector  locking''  (also  "electric  detection")  and  is  defined 
as  being  "electric  locking  effective  while  a  train  occupies  a  given 
section  of  a  route,  and  adopted  to  prevent  manipulation  of  levers 
that  would  endanger  a  train  while  it  is  within  that  section."  In 
section  locking,  track  circuits  and  relays  are  used  for  controlling 
electric  locks  on  the  switch  or  facing  point  lock  levers,  or  opening 
the  controlling  circuit  for  switches  to  prevent  their  being  thrown 
under  passing  cars,  a  function  for  which  detector  bars  were  orig- 
inally devised.  With  the  use  of  section  locking  the  track  circuits 
are  usually  extended  to  the  fouling  point  of  the  switch  controlled 
or  protected,  and  it  may  be  employed  in  lieu  of  detector  bars  or 
in  conjunction  with  them. 

The  Detector  Bar.  A  detector  bar  consists  of  a  bar  of  iron 
mounted  on  pivoted  links  alongside  on  the  outer  side  of  the  track 
rail  and  so  arranged  that  when  moved  longitudinally  the  bar  is 
lifted  higher  than  the  top  of  the  rail.  The  bar  is  so  connected 
to  the  switch  movement  that  it  must  be  lifted  before  the  switch 
is  moved.  If  any  pair  of  wheels  is  on  the  rail  the  bar  is  pre- 
vented .from  moving  by  coming  in  contact  with  the  wheel  thread, 
and  it  is  made  of  such  lengths  that  it  is  never  entirely  free  of  the 
wheels  of  any  car  standing  or  moving  over  it.  If  the  detector 
bar  cannot  move,  the  switch  cannot  be  moved  and,  consequently, 
the  detector  bar  will  prevent  the  switch  from  being  thrown  under 
a  car. 

The  Efficiency  of  the  Detector  Bar.  From  the  standpoint 
of  safety  the  inside  detector  bar — which,  contrary  to  the  outside 
detector  bar,  comes  in  contact  with  the  flanges  of  the  wheels — is 
vastly  superior.  They  are  objectionable,  however,  by  reason  of 
the  presence  of  switch  rods  and  other  track  accessories,  which 
prevent  their  being  placed  where  they  are  most  needed,  and  also 
on  account  of  the  wheel  flange  not  being  of  uniform  depth.  The 
introduction  of  rails  larger  than  85  lb.  section  having  wide  head 
ha?  lessened  the  former  efficiency  of  the  detector  bar,  as  the  bar 

85 


ELECTRIC   LOCKING 

when  thrown,  instead  of  striking  the  tread  of  the  wheel,  is  quite 
liable  to  pass  up  outside.  Furthermore,  at  power  interlocking 
plants,  if  a  detector  bar  is  prevented  from  being  thrown  due  to 
the  presence  of  a  car  moving  over  the  switch,  the  operation  of 
the  switch  lever  must  necessarily  injure  the  detector  bar,  due  to 
the  considerable  force  transmitted  to  the  switch  operating 
mechanism.  In  fact,  experience  has  proven  detector  bars  a  very 
uncertain  quantity  and  very  unreliable,  and  it  might  rightly  be 
said  that  they  are  designed  on  a  wrong  principle,  for  the  simple 
reason  that,  contrary  to  other  signal  appliances  which  are  so  de- 
signed that  a  failure  will  give  a  danger  indication,  a  detector  bar 
when  failing  is  inoperative. 

Section  Locking  Protection.  The  only  check  on  the  man- 
ner in  which  the  operator  handles  his  levers  at  a  plant  employing 
detector  bars  for  switch  protection  is  the  dog-locking  and  the 
detector  bar  and,  with  moderate  speed  of  trains  and  a  high  intelli- 
gence in  tower  operators,  it  has  proven  to  be  efficient,  and  noth- 
ing more  could  be  desired.  Increased  speed  and  the  consequent 
disastrous  results  which  would  ensue  should  the  throwing  of  a 
switch  under  a  train  lead  to  its  partly  running  off  a  derail  or 
through  a  sharp  turnout  at  high  speed,  has  caused  the  demand 
for  more  reliable  protection  along  this  line.  Thus,  to  overcome 
the  difficulties  and  dangers  just  related  and  also  for  other  rea-' 
sons,  such  as  trouble  with  snow  and  ice,  the  track  circuit  in  com- 
bination with  section  locking  as  a  substitute  for  the  detector  bar 
has  come  into  general  use.  This  class  of  electric  locking,  inas- 
much as  it  can  be  used  in  place  of  detector  bars,  can  be  consid- 
ered as  an  economy,  because  one  detector  bar  can  at  most  be  made 
to  protect  two  switches  if  they  are  close  together,  while  one  track 
circuit,  with  its  locks,  etc.,  can  displace  a  number  of  bars.  There- 
fore, in  most  cases  section  locking  is  not  only  cheaper  to  install, 
but  also  considerably  more  economical  to  maintain. 

Combined  Protection.  Detector  bars  are  often  employed  in 
connection  with  section  locking,  as  there  are  roads  which  do  not 
think  it  entirely  safe  to  depend  on  the  track  circuit  alone  for  pro- 
tection against  the  throwing  of  switches  and  derails  under  trains. 
there  being  numerous  instances  of  conditions  where  detector  bars 
can  hardly  be  dispensed   with.     This  is   particularly  true  when 

86 


SECTION     LOCKING 

guarding  against  slow  acting  relays,  so  as  to  preclude  all  possi- 
bility of  switches  being  thrown  in  front  of  trains  on  account  of 
track  relays  not  responding  quickly  when  shunted  due  to  sand 
on  rails,  rusty  rails,  poor  track  circuit  or  improper  relay  design. 
As  the  safe  operation  of  a  switch  from  careless  manipulation 
while  ^a  train  is  moving  over  it  (where  section  locking  only  is 
provided)  is  wholly  dependent  on  the  quick  action  of  the  track 
relay,  it  is  possible  before  the  lock  has  responded  that  at  least 
one  of  the  derails  in  the  route  could  have  been  thrown.  A  plant 
having  no  approach  or  stick-locking  should  at  least  main- 
tain one  detector  bar  for  the  switch  at  the  entrance  to  each  high 
speed  route.  At  power  interlockings  the  vibration  of  a  fast  mov- 
ing train  may  also  cause  the  accidental  operation  of  a  switch 
movement  sufficiently  to  unlock  it  unless  detector  bars  are 
employed. 

For  reasons  just  mentioned  and  also  to  act  as  a  check  upon 
the  track  circuit,  many  roads  in  this  country  are  today  using  both 
bars  and  track  circuits  for  switch  and  derail  protection. 

Special  quick  acting  relays  are  frequently  employed  on  very 
short  track  sections,  such  as  detector  bar  sections  where,  as  ex- 
plained, it  is  important  that  the  relay  respond  quickly. 

The  method  generally  employed  in  section  locking  is  to  divide 
the  track  circuit  through  the  interlocking  limits,  between  the 
home  and  dwarf  signal  into  as  many  convenient  sections  so  as  to 
allow  maximum  freedom  of  lever  movements  and  thereby  accom- 
modate switching  conditions. 

At  Mechanical  Plants.  Section  locking  at  a  mechanical 
inter-locking  plant  is  generally  applied 

(1)  By  the  employment  of  electric  locks  on  the  switch  and 
derail  levers  controlled  through  track  relays  in  the  sections 
involved. 

(2)  By  the  employment  of  electric  locks  on  the  facing  point 
lock  levers  that  lock  the  switches  in  the  section  and  controlled 
in  the  same  manner  as  the  locks  in  scheme  1. 

Schemes  1  and  2  are  alike  with  respect  to  the  control  of  the 
locks,  and  Fig.  83  shows  the  application.  Lock  "D,"  which,  ac- 
cording to  the  scheme  employed,  can  be  applied  to  either  lever 
4  or  5,  takes  battery  through  the  track  relay  "A"  and  a  lever 
circuit  controller  "E."     It  is  evident  that  as  a  train  is  occupying 

87 


ELECTRIC    LOCKING 

section  "A"  the  lever  is  locked  in  its  normal  or  reverse  positions, 
"F"  is  a  screw  release  often  introduced  into  the  circuit  to  allow 
the  towerman  to  make  a  change  of  route  should  the  track  circuit 
be  out  of  order.  There  are  roads  which  consider  it  undesirable 
to  use  any  release  at  all  where  the  section  locking  takes  the  place 
of  detector  bars  when  bars  are  not  used.  They  claim  that  if  a 
release  is  provided  it  is  possible  to  operate  it  while  a  train  is  on 
the  track  circuit  with  grave  dangers  of  a  derailment.  It  cannot  be 
denied,  however,  that  even  with  the  most  careful  maintenance  an 
occasional  failure  of  the  track  circuit  is  unavoidable,  and  in  such 
cases  it  is  a  definite  advantage  that  the  leverman  with  his  intelli- 
gence may  act  as  an  immediate  substitute  for  the  appliance  which 
has  broken  down  and  therebv  avoid  continuous  delay  in  traffic. 


Signal  control. 


FIG.  S3. 


With  the  use  of  detector  bars  there  will  also  be  occasional 
break  downs  and,  as  this  may  prevent  the  change  of  a  route,  with 
consequent  congestion  and  delay  to  traffic,  there  is  only  one  rem- 
edy, namely,  to  temporarily  have  them  disconnected.  With  no 
release  it  is  necessary  to  provide  a  key,  placed  in  a  key  box,  with 
which  the  leverman  can  unlock  the  lever  lock  and  operate  it  by 
hand.  With  this  method,  however,  the  leverman  has  access  to 
the  lever  lock  until  the  key  is  again  replaced  in  the  box  by  the 
maintainer.     (See  Chapter  XIV). 

In  order  that  the  operator  will  again  return  the  release  normal, 
the  normal  contact  on  the  release  should  be  used  for  the  signal 
control  if  the  signal  is  electrically  controlled,  and  if  mechanically 
controlled  the  release  must  be  an  electro-mechanical  screw  release 
which  when  reversed  would  effect  the  mechanical  locking  of  all 
signals  governing  over  the  route  in  their  normal  positions. 

Locks  ox  Facing  Point  Lock  Levers  Versus  Switch 
Levers.     The  employment  of  full  normal  and  full  reverse  locks 

88 


SECTION     LOCKING 

on  facing'  point  lock  and  derail  levers  is  advocated  by  some  engi- 
neers for  the  reason  that  it  will  act  as  a  check  on  the  track  circuit, 
but  the  practice  is  not  to  be  recommended  because  the  safe  rever- 
sal of  a  facing  point  lock  and  derail  lever  should  only  depend 
upon  the  mechanical  locking  in  the  machine  and  the  condition 
of  the  switches  which  they  lock,  while  the  protection  the  lever 
lock  should  give  is  the  placing  of  the  lever  normal  while  a  train  is 
passing  over  the  functions.  Besides  the  normal  position  of  these 
levers  is  an  inactive  position,  as  it  does  not  lock  nor  prevent  con- 
flicting routes  to  be  lined  up.  The  practice  may  furthermore  lead 
to  unnecessary  delays  in  case  of  derangements.  The  employment 
of  a  normal  and  reverse  lock  on  the  F.  P.  L.  lever  has  the  advan- 
tage of  the  additional  protection  secured  thereby.  At  interlock- 
ings  semi-automatic  signals  are  given  full  track  circuit  and 
fouling  protection,  while  no  such'  protection  is  given  slow  speed 
and  dwarf  signals.  By  having  the  locking  of  the  F.  P.  L.  lever 
lock  also  take  effect  with  the  lever  at  normal,  the  reversal  of  this 
lever  and  the  consequent  clearing  of  any  signal  is  prevented  unless 
the  track  circuits  are  in  order  and  all  fouling  circuits  clear  of 
any  obstruction. 

In  a  track  lay-out  one  facing  point  lock  lever  is  often  employed 
to  lock  several  switches,  and  hence  it  will  prove  a  more  economical 
arrangement  to  place  the  locks  on  that  lever.  It  should  be  noted, 
however,  that  locks  on  the  facing  point  lock  levers  do  not  give 
full  section  locking  protection,  as  it  is  possible  for  the  operator 
to  line  up  a  route  without  reversing  any  lock  lever  and  give  the 
engineman  a  hand  signal  or  card  to  proceed,  with  no  protection 
whatever.  It  is  evident  that  this  could  not  occur  with  the  locks 
on  the  switch  and  derail  levers. 

"SS"  Circuits.  When  "SS"  relay  circuits  are  employed  (see 
Chapter  IV)  section  locking  can  be  accomplished  by  placing  the 
lever  lock  on  the  F.  P.  L.  lever  and  the  circuit  arranged  as  shown 
in  Fig.  84.  With  this  arrangement  indication  locking  as  well  as 
section  locking  is  provided  by  a  very  simple  circuit  arrangement. 
The  F.  P.  L.  lever  must  be  equipped  with  a  normal  and  reverse 
lever  lock  in  this  case :  the  normal  locking  part  to  provide  indica- 
tion locking  for  the  switch  and  the  reverse  locking  for  section 
locking  protection.  Section  locking  takes  place,  however,  with 
the  normal  and  reverse  position  of  the  F.  P.  L.  lever.     If  it  is 

89 


ELECTRIC   LOCK  IXC, 


deemed  undesirable  to  have  this  protection  the  circuit  can  be 
arranged  as  in  Fig".  85,  where  the  F.  P.  L.  lever  lock  is  controlled 
through  the  track  relay  only  when  the  lever  is  reversed,  while  the 
normal  control  breaks  through  the  "SS"  relay  only. 


FPL. 4- 


£ 


FPL  A      3 

U    1             ^ 

M 
0 


f£ 


SS  REIAY 
FOR  SW 


n 


s 


for  Syv  3 


n 


M"  t 


— _B_+ 


FIG.  84. 


FIG.  85. 


At  Power  Plants.     The  schemes  are  as  follows : 

( 1 )  Protection  is  obtained  by  the  employment  of  separate 
electric  locks  (in  addition  to  the  regular  indication  lock)  on  the 
switch  and  derail  levers  and  have  them  controlled  as  at  a  mechan- 
ical plant. 

(2)  By  the  employment  of  a  relay  (generally  termed  lock 
relay  and  sometimes  lock  indicator)  which  is  controlled  by  the 
track  relay  for  the  section  involved  and  through  which  is  broken 
the  control  circuit  (the  positive  side)  for  the  switches  and  derails 
in  the  particular  section  of  track. 

(3)  A  combination  of  both  the  above  mentioned  schemes. 

(4)  P>y  a  modification  of  the  indication  lock  segment  and  by 
having  the  indication  wire  in  certain  positions  of  the  lever  con- 
trolled through  the  track  relay  in  the  section  where  a  switch  or 
derail  is  located. 

The  control  of  the  locks  in  these  schemes  is  usually  accom- 
plished through  the  medium  of  an  indicator  or  repeater.  This  is 
done  in  order  to  give  visual  indication  of  the  condition  of  the 
track  section  and  not  compel  the  operator  to  depend  upon  watch- 
ing the  train  or  trying  his  levers.  Repeated  trials  will  in  time 
wear  out  the  dog  and  the  slot  or  segment  of  the  lock. 

Fig.  86  illustrates  scheme  1.  The  track  relay  "A"  controls 
the  indicator  "G,"  which  in  turn  controls  the  lever  locks  for  the 
derails  and  switches  in  track  section  "A."  The  signal  bus  bar 
is  cut  into  as  many  separate  sections  as  are  desirable  for  proper 

90 


SECTIOX     LOCKING 

operation  of  the  plant  and  the  signal  bus  feed  wire  from  the 
operating  switch  board  is  broken  through  a  normal  contact  on  the 
screw  release  to  insure  its  being  restored  normal.  The  circuit 
may  be  arranged  so  that  the  reversal  of  the  screw  release  will 
cause  the  energization  of  the  indicator,  and  in  many  cases  this 
arrangement  will  prove  more  satisfactory. 


Feeder  for  signal 
bus  bar 


Scheme  2  is  represented  in  Fig.  87.  The  switch  bus  bar  is  cut 
into  as  many  sections  as  there  are  track  sections  at  the  plant,  each 
bus  bar  section  being  controlled  through  a  contact  on  the  track 
indicator  and.  if  desired,  through  a  closed  point  on  the  screw 

5  *~ 


5-a 


Switch  bus  feeder: 
Signal  bus  feeder. 


FIG.  87. 


release.  Thus,  this  arrangement  accomplishes  the  same  purpose 
as  a  lock  on  the  lever  because  the  dropping  of  the  indicator  will 
cut  current  off  from  the  switch,  and  while  not  permitting  the 
partial  reversal  of  the  lever  when  a  train  is  on  the  track  circuit, 
it  will  prevent  the  switch  from  being  thrown,  owing  to  the  inter- 
ruption of  the  current  supply. 


Lock  Relays  Versus  Lever  Locks.  Opinions  differ  as  to 
which  one  of  the  schemes  described  offers  the  most  advantages. 
There  are  engineers  who  have  taken  the  stand  that  locks  on  the 
levers    should    always    be    used.      Their    reasons    are    numerous. 

91 


ELECTRIC    LOCK  IXC 

Cases  have  been  known  where  the  breaking  of  the  switch  bus 
feed  circuit  was  employed,  where  switches  have  opened  under 
trains  simply  because  the  control  circuit  on  which  the  integrity 
of  the  route  depended  was  open.  This  may  be  explained  as 
follows : 

In  electric  interlocking  the  position  of  the  switch  may  often 
depend  upon  the  integrity  of  the  control  circuit,  because  the  cir- 
cuit is  so  arranged  that  if  a  switch  should  start  to  open  before 
it  can  unlock  completely  the  circuit  is  thrown  onto  the  operating 
circuit  controller,  which  drives  the  switch  back  and  puts  it  in 
proper  position  again.  If  the  circuit  in  such  cases  was  inter- 
rupted there  would  be  nothing  to  prevent  the  switch  point  from 
completely  opening,  with  disastrous  results  to  a  train  moving 
over  it.  Opponents  rightfully  maintain  that  if  a  facing  point 
switch  is  liable  to  partly  open  under  a  train  the  result  is  prac- 
tically the  same,  the  circuit  being  interrupted  or  not.  This  much 
may  be  said,  however,  in  favor  of  an  uninterrupted  switch  control 
circuit :  Should  a  train  approaching  a  switch  partly  open  the 
switch  through  the  vibrations  of  the  track,  the  switch  might  be 
set  right  again  by  the  aid  of  an  uninterrupted  circuit.  While  the 
train  is  on  the  switch  a  detector  bar  will  prevent  the  unlocking  of 
the  switch.  An  occurrence  of  this  kind,  which,  by  the  way,  for- 
tunately seldom  happens,  can  only  be  prevented  by  the  use  of  an 
electric  bolt  lock  and  partly  remedied  by  the  use  of  a  detector 
bar,  which  must  be  raised  before  the  switch  can  be  unlocked. 
Another  objection  to  scheme  2  is  the  ability  of  the  operator  to 
reverse  the  switch  lever  as  far  as  to  the  reverse  indicating  posi- 
tion with  a  train  in  the  section  and  in  distraction  leave  the  lever 
in  this  position.  Immediately  upon  the  picking  up  of  the  indi- 
cator current  will  be  applied  to  the  switch  and  cause  its  reversal, 
which  may  have  a  disastrous  result  should  a  maintainer  or  a  sec- 
tion gang  be  working  at  this  location.  This,  of  course,  is  of 
minor  importance  and  has  nothing  to  do  with  section  locking  as 
a  protection  to  train  movements,  but  it  may  be  typical  of  some 
of  the  points  to  be  considered  when  choosing  a  certain  style  of 
locking  scheme. 

With  the  use  of  lock  relays  it  has  happened  that  while  a  switch 
movement  is  operated  a  train  or  an  engine  has  approached  the 
switch  closely  enough  so  as  to  de-energize  the  lock  relay,  thereby 
preventing  the  full  reversal  or  the  placing    of    the    switch    full 

92 


SECTION     LOCKING 

normal  by  cutting  the  current  supply  off.  This  has  caused  the 
switch  to  remain  in  a  middle  position,  which  could  not  have  hap- 
pened with  the  use  of  lever  locks.  An  occurrence  of  this  kind 
may  also  cause  the  arching  of  the  relay  points  breaking  the  110 
volt  circuit.  It  is  necessary  to  employ  relays  having  contacts  ca- 
pable of  carrying  and  breaking  heavy  currents  and  in  some  ca.-^  5 
a  magnetic  blow  out.  Lock  relays  will  also  to  a  certain  extent 
complicate  arrangements  when  used  in  connection  with  route 
locking  of  a  plant  where  individual  locks  on  the  switch  levers 
would  greatly  simplify  the  application  of  the  protective  circuits. 
Still  another  objection  to  the  breaking  of  the  switch  control  is 
the  possibility  of  an  accidental  bridging  of  the  positive  signal  and 
switch  bus  bar,  or  the  liability  of  the  operator  attempting  to 
"beat"  the  section  locking  with  a  failure  of  the  track  circuit. 
With  the  use  of  lever  locks  no  cutting  or  separation  from  other 
positive  busses  of  the  switch  bus  bars  is  necessary. 

Terminal  Protection.  Fig.  88  shows  section  locking  as 
applied  to  a  terminal.  To  facilitate  the  handling  of  trains  the 
track  circuit  is  cut  into  three  sections,  "A,"  "B"  and  "C."  The 
cutting  of  the  switch  bus  is  performed  in  the  regular  way,  as 
explained  in  connection  with  Fig.  87,  to  permit  maximum  free- 


m 


SlQ.+ 


Switch  bus 
Signal  bus 


FIG.   88. 


dom  of  lever  movements.  In  order  to  obtain  full  protection  so 
that  the  reversal  of  the  screw  release  for  any  one  of  the  sections 
will  prevent  the  clearing  of  a  signal  governing  a  route  lined  up 
over  it,  unless  the  release  is  placed  normal  again,  it  has  necessi- 
tated the  selecting  of  some  of  the  signal  bus  feed  wires.  As  an 
example,  take  signal  bus  bar  1.     Should  track  relay  for  section 

93 


ELECTRIC    LOCKINC 

"l  "  be  inoperative  for  some  reason,  the  reversal  of  the  screw 
release  "C"  will  permit  the  operation  of  the  switch  to  its  desired 
position.  It  should  be  evident  that  it  would  not  do  to  have  the 
operator  clear  signal  1  while  switches  2  and  3  were  normal  and 
screw  release  "C"  reversed.  If  signal  1  was  not  broken  through 
this  release  with  the  mentioned  line-up  of  switches,  track  relay 
"i  "  could  be  shunted  out  of  the  switch  circuit  permanently  with- 
out interfering  with  the  clearing  of  signal  1.  It  should  also  be 
evident  that  with  switch  3  reverse,  signal  1  should  not  be  con- 
trolled through  release  "C,"  as  this  would  tie  up  traffic  to  some 
extent.  Thus,  signal  bus  bar  1  is  broken  through  all  the  releases 
in  series,  shunted  out  of  release  "C"  when  switch  3  is  reversed 
and  out  of  release  "B"  when  switch  2  is  reversed,  while  it  breaks 
tli rough  release  "A"  all  the  time.  As  the  other  signals  only  gov- 
ern one  section  their  bus  bars  are  only  broken  through  one  screw 
release.  It  should  be  unnecessary  to  show  a  layout  employing 
locks  on  the  levers,  as  the  application  will  be  identically  the  same. 

Combined  Protection.  The  reason  for  desiring  double  pro- 
tection by  the  use  of  lock  Telays  and  lever  locks  is  first  to  insure 
that  in  case  the  lock  relay  should  fail  to  respond  quickly  the  lever 
lock  is  depended  upon  to  effect  the  section  locking,  and  vice 
versa.  Invariably  the  lock  relay  and  the  lever  lock  should  both 
be  controlled  through  the  track  relay. 

Section  Locking  for  Electro-Pneumatic  Plant.  Section 
locking  at  an  electro-pneumatic  and  style  "F"  plant  is  accom- 
plished through  the  indication  magnets.  As  the  two  lockings, 
indication  and  section  locking,  are  never  required  at  the  same 
time,  they  can  be  secured  by  the  use  of  the  same  apparatus 
through  a  modification  of  the  lock  segment,  in  addition  to  the 
circuits  controlling  the.  indication  magnets.  In  Fig.  89  the  arma- 
ture "B"  of  the  normal  indication  magnet  engages  one  side  of 
dog  "A"  for  section  locking  purposes.  With  the  lever  in  the  ex- 
treme normal  position  as  shown  the  circuit  for  the  section  lock- 
ing starts  from  positive  battery,  front  contact  on  the  track  relay, 
wire  2,  latch  contact  "C,"  wire  3,  circuit  controller  "D"  and  mag- 
net "X"  to  common,  thereby  energizing  "N"  and  raising  arma- 
ture 'TV  from  engagement  with  "A,''  which  unlocks  the  lever. 
With  the  lever  in  the  extreme  reverse  position  current  for  magnet 

94 


SECTION     LOCKING 


"R"  must  pass  through  the  same  relay  and  controller  "D"  re- 
versed. The  dog  "J"  engages  with  the  armature  of  "R"  when 
the  lever  is  reversed  in  the  same  manner  as  "A"  with  armature 
at  "X"  when  normal. 


N.l 


Rl 


^*=ifes| 


6+ 


FIG.  89. 

Electric  Bolt  Lock.  As  an  indication  for  switches  at  a  me- 
chanical interlocking  plant  the  bolt  lock  is  provided,  through 
which  the  pipe  connected  signals  are  controlled  to  insure  the 
switch  being  in  the  proper  position  for  the  clearing  of  the  signal. 
The  bolt  lock,  however,  is  cumbersome  and  expensive  to  apply 
to  any  but  a  few  switches  in  the  route,  and  without  the  bolt  lock 
dependence  must  be  placed  upon  the  facing  point  lock  altogether 
with  results  that  may  be  betrayed  in  a  number  of  different  ways ; 
pins  can  work  out,  cranks  and  compensators  work  loose  from 
their  foundation  and  the  foundations  move.  The  lock  rod  or 
plunger  or  any  part  of  the  mechanism  can  be  removed,  as  in 
making  repairs,  and  the  working  of  the  lever  is  not  affected.  In 
other  words,  nearly  any  failure  through  breakage,  removal  of  a 
part,  or  bv  the  reason  of  lost  motion  is  dangerous  and  not  on  the 
side  of  safety.  In  electric  interlocking  no  electric  bolt  lock  is 
necessary,  as  a  switch  must  be  fully  thrown  and  locked  before  an 
indication  can  be  secured  at  the  lever.  Here  the  possibility  of 
vibrations  .opening  the  point  must  be  considered,  and  a  bolt  lock 
would  prevent  this.  To  make  protection  complete  an  electric 
bolt  lock  should  fulfill  the  following  requirement :  The  governing 
signal  when  clear  shall  lock  the  switch  in  position  and  the  switch, 
when  unlocked,  shall  place  and  hold  the  signal  in  the  stop  posi- 
tion. This  is  accomplished  by  having  an  electric  lock,  situated  at 
the  switch,  arranged  so  that  when  de-energized  an  armature  or 

95 


ELECTRIC   LOCKINC 


dog  drops  into  a  notch  in  the  end  of  the  locking  plunger  and 
closes  the  circuit  when  raised  out  of  the  notch  or  when  dropped 
below  it,  due  to  the  absence  of  the  plunger  the  circuit  should  be 
open. 

Fig.  90  shows  an  electric  bolt  lock  circuit  as  applied  to  a  switch 
where  a  mechanical  signal  governs  over  it,  which  will  give  sec- 


B  Ap. 


n: 


5 


5 


Bolt  /ocAtt 
B 


Jl 


FIG.  90. 


¥ 


tion  locking  in  addition  to  preventing  the  operation  of  the  switch 
while  the  signal  is  clear.  The  signal  lever  is  equipped  with  a  full 
normal  lock  "E,"  which  prevents  any  manipulation  of  this  lever 


J 

m 2^ 

XL 

i It*     o  o 

11 1 1& 

il: 

R    A$. 

* 

c 

l 

%lt  locktt 

£ 

B 

Si  anal control . 

\ 

FIG.  91. 


while  the  switch  is  being  operated.     Fig.  91  shows  the  circuit  as 
applied  to  a  power  operated  signal. 

Track  Circuit  Layouts.  From  what  has  been  said  in  the 
present  article  and  under  "The  Track  Circuit"  it  should  be  evi- 
dent that  in  a  general  layout  of  track  circuits  it  is  advisable  to 
have  the  insulated  joints  not  only  located  so  as  to  conform  to 
standard  practice  of  the  road,  but  also  to  have  the  track  sections 
so  related  to  each  other  that  the  best  result  will  be  obtained  from 
a  track  or  operating  standpoint,  and  have  them  so  inter-related 
that  the  best  result  will  be  obtained  with  a  full  knowledge  of  the 
effects  produced  for  a  proper  and  full  protection  of  such  a  lay- 
out. While  this  would  perhaps  be  most  preferable  it  is  not  al- 
ways practicable,  so  that  the  locking  and  dog  sheets  should  be 
consulted  and,  if  necessary,  revised  with  the  object  in  view  to 

96 


SECTION     LOCKING 

avoid  undue  complications  in  the  track  circuit  arrangements,  and 
also  add  to  the  protection  provided  by  the  track  circuit,  or  pro- 
cure protection  where  the  track  circuit  should  fail  to  give  such. 

When  designing  a  track  circuit  for  a  certain  location  it  makes 
a  vast  difference  if  the  track  circuit  is  provided  for  the  semi- 
automatic control  (slotting  control)  of  the  signals,  and  if  it  in 
addition  also  is  used  for  section  locking  purposes.  Take,  for 
example,  Fig.  92,  showing  a  part  of  an  interlocking  plant,  assum- 


^ 

^>-^     /iSr 

"^ — j>-^i — 

t    ^T~    y 

a . — *  ■ — 

~^r-a    r— sia — c^ 

^=^^^-      ' 

(, ,. 

FIG.   92. 

F 


ing  this  to  be  a  plant  not  employing  section  locking.  It  will  be 
necessary  to  cut  the  upper  track  into  two  track  sections  "A"  and 
"B"  in  order  that  a  movement  from  "D"  to  "E"  will  not  prevent 
the  clearing  of  signal  "K"  for  a  movement  from  "F"  to  "G"  over 
"I"  reversed.  In  other  words,  to  permit  parallel  train  move- 
ments to  take  place,  a  train  standing  in  section  "A"  in  the  rear 
of  the  dwarf  signal  "J"  will  not  interfere  with  the  manipulation 
of  lever  for  switch  "H,"  no  section  locking  being  provided.  With 
section  locking  the  upper  track  must  be  divided  into  three  sec- 
tions, an  additional  cut  opposite  dwarf  signal  "J"  being  necessary. 
The  necessity  of  cutting  section  "A"  into  two  sections  is  to  per- 
mit the  manipulation  of  switch  lever  "H"  while  a  train  is  standing 
in  the  rear  of  dwarf  signal  "J."  the  lever  locks  or  switch  buses 
being  controlled  through  the  track  relay. 

It  has  been  stated  that  for  full  section  locking  protection  every 
particle  of  track  between  the  home  and  dwarf  signals  at  an  inter- 
locking plant  should  be  provided  with  track  circuits,  either  in  the 
form  of  main  circuits  or  fouling  circuits.  In  places  where  the 
track  circuits  are  employed  for  slotting  purposes  only,  fouling 
protection  is  equally  necessary,  but  this  protection  does  not  neces- 
sarily have  to  be  carried  as  far  back  as  to  the  dwarf  signal.  For 
a  proper  concerption  of  this  two  turnout  circuits  will  be  shown. 

Fig.  93  shows  a  turnout  provided  with  a  shunt  fouling  used 
in  connection  with  a  plant  not  employing  section  locking.  The 
derail  "A"  is  located  at  the  fouling  point  and  the  carrying  of  the 
fouling  circuit  thus   far  is   sufficient.     This  will  be  evident   for 

97 


ELECTRIC   LOCKING 

reasons  that  for  the  switch  protection  the  detector  bar  covers  the 
distance  between  the  signal  and  the  derail.  Thus,  should  an 
engine  proceed  past  the  signal  as  far  as  the  derail,  with  the  derail 
normal,  it  will  be  derailed,  and  should  it,  while  the  derail  is  re- 
versed, remain  between  the  derail  and  the  signal,  the  detector 
bar  will  prevent  the  main  switch  from  being  lined  up. 

A  plant  employing  section  locking  should  have  a  turnout  pro- 
tection as  shown  in  Fig.  94.  Here  the  fouling  protection  is  car- 
ried back  to  the  dwarf  signal.  While  it  is  not  strictly  necessary 
to  carry  the  fouling  protection  as  far  as  to  the  dwarf,  it  is  neces- 
sary to  carry  it  past  the  derail  for  the  switch  protection.  The 
intervening  few  feet  between  the  dwarf  and  the  switch  are  gen- 
erally included  in  the  circuit  as  an  additional  protection  when 


FIG.   93. 


FIG.    94. 


FIG.  96. 


section  locking  only  is  employed,  and  as  a  necessity  when  section 
locking  in  connection  with  the  route  locking  is  employed. 

Fig.  95  shows  a  track  layout  of  two  main  tracks  and  a  siding, 
with  track  circuit  applied  for  signal  slotting  purposes.  The  two 
main  tracks  .each  comprise  one  track  section  "A"  and  "P>." 
Fouling  protection  is  provided  on  crossover  between  siding  and 
track  "A."  Fig.  96  shows  the  same  layout  when  a  track  circuit 
used  for  section  locking  purposes  is  applied  to  it.  Here  four 
track  sections  are  necessary,  "A"  and  "C,"  in  order  to  accommo- 
date parallel  movements  over  crossovers  "E"'  and  "F"  simul- 
taneously, and  "D"  is  added  to  provide  full  section  locking  pro- 
tection for  crossover  "F." 

98 


SECTION     LOCKING 

Important  Fouling  Protection.  It  should  be  evident  from 
foregoing  examples  that  four  track  sections  are  necessary  in  the 
layout  Fig.  97.    The  three  main  tracks  must  be  operated  so  as  to 


c/i  \E 


allow  parallel  movements  and,  in  addition,  the  middle  track  must 
be  cut  between  the  crossovers  to  permit  trains  to  pass  from  track 
"A"  to  "B"  and  from  "C"  to  "D"  simultaneously.  The  solution 
of  the  problem  would  apparently  be  to  place  insulated  joints  in 
the  track  at  "E,"  this  being  equally  distant  from  switch  point 
"F"  and  "G."  These  distances,  however,  are  often  so  short  that 
it  would  be  possible  to  have  a  train  move  from  track  "A"  to  "B" 
with  crossover  "F"  reversed,  while  an  engine  or  car  standing  at 
"H"  within  the  limits  of  the  track  section  "C"  would  foul  with 
the  crossover.  The  simplest  way  to  prevent  an  occurrence  of  this 
kind  (assuming  the  joints  were  placed  at  "E")  would  be  to  have 
the  mechanical  locking  in  the  interlocking  machine  so  arranged 
that  when  switch  "F"  is  reversed  switch  "G"  would  also  have  to 
be  reversed.  In  other  words,  let  lever  for  switch  "F"  reversed 
lock  lever  for  switch  "G"  reversed.  Thus,  with  a  car  standing  at 
"H"  it  would  not  be  possible  to  reverse  lever  "G,"  the  lock  on 
the  lever  preventing  it,  being  controlled  through  the  track  circuit 
"C,"  and  consequently  it  would  be  impossible  to  reverse  lever 
"F."  Even  with  this  precaution,  however,  it  might  be  possible 
to  have  a  car  stand  at  "J"  and,  reversing  switch  "G,"  have  a  train 
pass  from  "G"  to  "D,"  sideswiping  car  "J." 

It  will  be  evident  that  no  mechanical  lever  locking  will  take 
care  of  this  condition,  because  it  would  be  impossible  to  so 
arrange  the  locking  that  lever  "F"  reversed  would  lock  lever  "G" 
reversed,  and  vice  versa.  There  are  two  ways  to  overcome  the 
situation,  and  of  these  Fig.  97  presents  the  most  simple.  Here 
track  circuit  "B"  is  carried  as  far  as  practicable  toward  switch 
point  "G,"  and  track  circuit  "C"  commenced  at  that  point.  This 
arrangement  will  take  care  of  switch  "F"  because  a  train  cannot 
proceed  beyond  the  insulated  joints  at  "K,"  separating  track  sec- 

09 


ELECTRIC    LOCK  IXC, 


tion  "I>"  from  "C,"  without  causing  the  track  relay  "B"  to  drop, 
and  consequently  either  prevent  the  reversal  of  this  switch,  or,  if 
it  has  already  been  reversed,  cause  the  signal  governing  over 
switch  "F"  reverse  to  assume  the  stop  position.  In  order  to  pro- 
tect a  movement  over  switch  "G"  reverse  lever  "G"  must  lock 
lever  "F"  reversed. 

Another  way  to  take  care  of  the  situation  would  be  to  have  the 
lock  on  lever  "G,"  in  addition  to  being  controlled  through  sec- 
tion "C,"  also  controlled  through  section  "B"  while  switch  "F" 
was  normal,  and  the  same  in  regard  to  lever  lock  "F,"  having  it 
break  through  section  "C"  with  switch  "G"  normal.  The  insu- 
lated joints  may  then  be  placed  at  "E."  This  method,  however, 
cannot  be  applied  to  plants  where  not  only  section  locking,  but 
also  sectional  route  locking  is  employed. 

In  Fig.  98  two  parallel  turnouts  are  shown  crossing  main 
tracks.    While  the  circuits  applied  to  this  track  layout  do  not  dis- 


F1G.  98. 


play  any  special  features,  they  do  show,  however,  how  a  favorable 
and  well  protective  arrangement  can  be  made  of  a  complex  situa- 
tion with  a  minimum  number  of  track  sections.  The  present 
layout  is  arranged  so  that  parallel  train  movements  can  take  place 
from  "D"  to  "E"  and  from  "F"  to  "G"  at  the  same  time,  like- 
wise from  "H"  to  "J"  and  from  "K"  to  "E."  It  will  be  noted 
that  track  section  "A"  is  carried  straight  through  with  jumpers 
across  the  crossing  rails.  Section  "C"  could  have  been  arranged 
the  same  way,  but  better  protection  is  obtained  by  the  carrying 
of  this  circuit  to  the  crossing  and  then  to  the  end  of  the  turnout. 
It  will  be  observed  that  in  order  to  properly  arrange  the  transpo- 
sition it  was  necessary  to  transpose  circuit  "A"  at  the  center 
between  the  two  crossings. 

Precautions    in    Designs.     When    selecting   the    control    of 
lever  locks  through  levers  it  should  be  remembered  that  never 

100 


SECTIOX     LOCKING 


should  the  contacts  so  used  be  full  normal  or  reverse  contacts, 
for  the  reason  that  the  lock  controlled  and  consequently  also  the 
lever  would  be  dependent  upon  the  proper  operation  of  the  func- 
tion through  which  it  is  selected  for  its  manipulation.  Thus, 
should    it    be    desired    to    have    switch  1  in  Fig-.  99a  controlled 


Track  relau. 


Bh-^-At^B 


~71t5J 


B 


Hd) 


FIG.  99. 


C 


%l" 


through  track  section  "A"  when  crossover  2  is  reversed,  contacts 
closed  between  the  full  normal  or  reverse  position  and  the  indi- 
cation positions  should  be  employed.  It  is  evident  that,  should 
switch  2  fail  to  indicate,  thereby  leaving  lever  2  in  the  middle 
position,  this  should  not  prevent  the  operation  of  switch  1,  as  it 
may  tie  up  traffic  for  a  considerable  length  of  time.  Of  course, 
the  lock  on  lever  2  is  controlled  through  sections  "A"  and  "B." 

A  lock  relay  should  never  be  without  current  except  when  the 
controlling  relay  is  de-energized.  This  will  be  evident  when  re- 
ferring to  Fig.  15a,  assuming  the  same  protection  to  be  desired 
as  when  lever  locks  were  employed.  It  would  not  do  to  arrange 
the  circuit  as  shown  in  Fig.  99b,  where  lock  relays  are  employed, 
because  it  is  always  possible  to  manipulate  the  lever  between  the 
normal  and  reverse  indication  positions.  Furthermore,  it  is  pos- 
sible to  reverse  levers  1  and  2  at  the  same  time.  Thus,  while 
the  leverman  may  operate  lever  1,  he  may  also  reverse  lever  2. 
This  would  cut  current  off  lock  relay  "B"  and  in  turn  off  switch 
1,  which  is  broken  through  relay  "B,"  and  thereby  leave  switch 
in  a  half  reverse  position  until  lever  2  is  completely  reversed. 
An  occurrence  of  this  kind  will  also  cause  the  arcing  of  the  con- 
tacts breaking  the  high  voltage  operating  circuit  for  switch  2. 

101 


ELECTRIC    LOCKING 

The  circuit  shown  in  Fig.  99c  should  not  be  employed  (one 
contact  makes  before  the  other  breaks)  because  lever  2,  being 
reversed  and  with  a  train  in  track  section  "A,"  it  is  possible  to 
place  lever  2  normal  as  far  as  to  the  normal  indicating  position, 
which  would  thereby  shunt  out  track  relay  "A,*  thereby  partly 
removing  the  protection  which  was  intended. 

Fig.  99d  shows  the  correct  solution  of  the  problem,  and  here 
the  lock  relay  is  controlled  in  series  through  track  relays  "A" 
and  "B"  and  shunted  out  of  relay  "B"  when  lever  2  is  full  normal. 
Should  it  be  desired  to  also  use  the  same  contact  on  track  relay 
"A,''  an  arrangement  as  shown  dotted  in  Fig.  99d  could  not  be 
used,  as  when  lever  2  was  normal  lock  relay  "A"  would  be 
shunted  out  of  track  relay  "A."  Ingenious  circuit  designers  have 
solved  this  problem  by  connecting  the  circuit  as  shown  in  Fig. 
99e,  one  contact  to  make  before  the  other  breaks.  This  arrange- 
ment would  be  all  right  as  far  as  lock  relay  "B"  is  concerned 
because  lever  2  would  have  to  be  full  normal  before  this  relay 
was  shunted  out  of  track  relay  "A."  Should  lever  2  be  left  in  a 
position  as  shown  in  99f,  it  is  possible,  however,  for  the  oper- 
ator to  circumvent  the  section  locking  and  release  lock  relay  "A" 
even  with  the  track  relay  de-energized,  and  thus  release  other 
switches  which  may  be  controlled  through  the  same  relay.  The 
sketch  99f  shows  a  different  symbol  for  the  lever  contacts  in  order 
to  make  the  error  clear.  The  only  way  to  prevent  this  is  to  use 
separate  relay  contacts  for  each  lock  relay. 

Conclusion.  It  will  be  seen  from  the  foregoing  that  section 
locking  is  merely  an  extension  of  the  function  of  the  track  cir- 
cuit and  that  proper  protection  cannot  be  obtained  through  a  per- 
fect design  of  the  locking  circuit  itself  without  a  track  circuit  that 
is  also  perfectly  designed.  It  will  also  be  noted  that  a  track 
circuit  only  cannot  provide  adequate  fouling  protection  without 
the  aid  of  section  locking.  It  will,  furthermore,  be  noted  that, 
while  detector  bars  only  protect  one  switch,  section  locking  covers 
a  track  section,  which  may  include  several  switches,  and  also  that 
if  a  detector  bar  fails  it  is  inoperative,  while  section  locking  will 
prevent  any  further  manipulation  of  levers  and  functions.  Sec- 
tion locking  will  also  compel  respect  for  dwarf  signals  and  make 
proper  switching  movements  imperative. 


102 


VI 

ROUTE    LOCK  IXC 

Definition.  Route  locking,  as  defined  by  the  Railway  Signal 
Association,  is  "Electric  locking  taking  effect  when  a  train  passes 
a  signal  and  adapted  to  prevent  manipulation  of  levers  that  would 
endanger  the  train  while  it  is  within  the  limits  of  the  route  en- 
tered." This  definition  might  easily  convey  the  conception  that 
the  protection  provided  must  necessarily  include  provisions 
against  the  throwing  of  switches  and  derails  under  a  train  while 
it  is  moving  over  them.  This,  however,  is  not  the  case,  as  many 
schemes  provide  protection  to  a  train  from  the  clearing  of  routes 
only,  permitting  other  train  movements  over  intersecting  tracks — 
in  other  words,  simply  grade  crossing  protection.  Route  locking 
as  applied  to  junction  points  and  terminals,  however,  is  in  most 
cases  a  development  of  section  locking,  being  modified  to  lock  all 
switches  and  derails  in  a  complete  route  from  the  time  the  train 
enters  until  such  time  as  the  route  is  cleared.  It  will  be  recalled 
that  section  locking  provided  protection  while  a  train  was  moving 
over  one  track  section  only. 

Purpose  of  Route  Locking.  At  an  interlocking  plant  where 
no  route  locking  is  provided  the  possibility  always  exists  that  the 
leverman,  before  the  train  has  entirely  cleared  a  route,  will  line 
up  a  conflicting  or  intersecting  route  for  a  train  movement  which 
may  cause  a  derailment  or  a  collision  and  a  consequent  wreck, 
because  there  would  be  no  physical  check  on  the  leverman  which 
would  prevent  an  occurrence  of  this  kind.  The  purpose  of  route 
locking  is,  therefore,  to  prevent  such  a  contingency  through  the 
medium  of  locking  devices,  either  applied  to  the  functions  over 
which  the  train  is  moving  or  to  the  functions  on  tracks  inter- 
secting the  track  to  be  protected.  A  designer  of  electric  locking 
circuits  should  always  bear  in  mind  that  the  protection  to  be  pro- 
vided should  not  duplicate  or  supersede  the  mechanical  dog 
locking  in  the  interlocking  machine.  However,  it  might  be 
applied  to  advantage  as  a  check  on  indication  locking  where 
power  operated  units  are  employed.  With  this  in  mind  route 
locking  will  resolve  itself  into  a  very  simple  proposition. 

Route  locking  proper  may  be  said  to  contain  the  basic  prin- 
ciples upon  which  all  styles  of  electric  locking  are  designed.     It 

103 


ELECTRIC    LOCKING 

might,  furthermore,  he  said  that  the  style  of  electric  locking 
applicable  at  different  locations  varies  as  to  the  kind  of  an  inter- 
locking plant  to  which  it  is  applied.  Interlockings  are  generally 
installed 

(  a)  For  the  protection  of  intersecting  tracks,  grade  crossings 
and  drawbridges. 

I  1))  For  the  safe  and  expeditions  handling  of  traffic  at  junc- 
tions for  two  or  more  roads. 

i  c  )  For  the  safe  and  expeditious  handling  of  trains  at  train- 
directing  or  traffic-assorting  points,  such  as  yards  and  terminals. 

A  combination  of  the  above  is  often  installed,  and  in  these  cases 
the  protection  must  necessarily  include  the  requisite  protection 
combined.  Broadly  speaking,  route  locking  may  be  divided  into 
two  classes,  viz.,  (a)  where  it  is  applied  to  protect  a  train  from 
the  clearing  of  conflicting  routes,  and  (b)  where  it  is  applied  to 
protect  the  route  occupied  by  the  train. 

Requirements.  (1)  Route  locking  should  invariably  be 
made  effective  with  a  train  entering  the  first  section  of  a  route. 

(2)  The  route  may  start  at  the  distant,  home  or  dwarf  sig- 
nal, depending  upon  local  conditions  and  the  protection  desired. 

(3)  Route  locking  can  be  made  effective  in  one  direction  on 
a  given  piece  of  track,  or  in  both  directions. 

(4)  Route  locking  may  be  made  effective  with  a  train  enter- 
ing a  route  with  the  signal  governing  the  route  at  danger  (the 
train  being  flagged  through),  or  with  the  signal  at  clear  only. 

To  simplify  diagrams  and  descriptions  all  schemes  presented 
will  give  route  locking  protection  for  train  movements  in  one 
direction  only,  it  being  understood  that  a  duplication  of  this 
arrangement  will  give  protection  for  movements  in  both  direc- 
tions. The  track  layouts  employed  to  illustrate  the  various  lock- 
ing schemes  are  also  arranged  in  the  simplest  form  possible  to 
the  purpose,  as  one  switch  or  signal  can  serve  quite  as  well  as  a 
greater  number,  which  would  only  tend  to  complicate  an  other- 
wise simple  presentation.  It  is  also  to  be  understood  that,  while 
a  circuit  might  be  shown  as  applied  to  a  mechanical  interlocking 
plant,  the  circuit  will  also  answer  the  purpose  for  a  power 
interlocking. 

104 


ROUTE   LOCKING 

Route  Locking  Protection  Only.  As  previously  stated, 
there  are  schemes  of  route  locking"  in  which  conllicting  routes 
are  the  only  ones  locked.  That  is,  while  a  train  has  entered  one 
route  it  accomplishes  the  locking  of  the  derails,  switches  or  signals 
of  the  conflicting  routes.  This  arrangement  is  used  only  at  rail- 
road grade  crossings,  but,  where  interlocked  derails  with  detector 
bars  are  employed  as  crossing  protectors,  it  can  hardly  be  con- 
sidered any  more  than  additional  dog  locking,  because  the  detec- 
tor bars  are  placed  for  the  purpose  of  preventing  the  intersecting 
route  from  being  cleared  while  a  train  is  on  them.  There  are 
places  where  it  is  advantageous  to  employ  route  locking  of  the 
style  mentioned  and  especially  where  the  traffic  of  one  road  is 
small  in  comparison  with  that  of  the  other ;  in  many  such  cases 
only  derails  are  placed  on  the  road  with  light  traffic  and  only 
signals  on  the  road  with  heavy  traffic. 

At  Non-Interlocked  Grade  Crossings.  At  grade  crossings 
between  two  steam  roads  or  a  steam  road  crossing  an  electric- 
road,  protection  is  often  provided  without  the  means  of  an  inter- 
locking plant.  This  arrangement  is  most  frequently  employed  in 
connection  with  a  grade  crossing  between  a  steam  and  electric 
road.  The  requirement  is  to  compel  the  conductor  on  the  electric 
car  to  proceed  to  the  crossing  so  as  to  observe  if  a  train  is 
approaching  before  the  route  can  be  set  to  allow  the  car  to  pass 
over  the  crossing.  As  the  steam  road  is  to  be  protected  by  the 
route  locking,  it  is  also  required  that  the  conductor  shall  not  leave 
the  crossing  until  the  apparatus  is  restored  to  normal  operating 
conditions.  This  is  the  most  primitive  style  of  route  locking,  but 
very  adequate  for  its  purpose,  and  is  illustrated  in  Fig.  100.    "E" 

rt  sod 


(a  I 


f 


tb) 

FIG.   100.  I-TG.   101. 

and   "H"  are   normally   closed  derails,   while  "F"  and  "G"  are 
normally  open  derails  on  the  electric  road.     Distances  "A"  and 

105 


ELECTRIC    LOCKING 

"D"  are  to  be  of  sufficient  length  to  allow  the  longest  car  to 
stand  there,  and  distances  "B"  and  "C"  can  be  three  to  four  rails 
in  length.  The  derails  are  operated  from  a  one-lever  stand  "I" 
at  the  crossing,  which  makes  it  necessary  for  the  conductor  to 
go  there  to  observe  if  a  train  is  approaching  before  a  car  is 
allowed  to  proceed  between  derails  "G"  and  "E,"  assuming  the 
car  to  be  moving  in  the  direction  of  the  arrow.  As  one  level- 
operates  all  the  derails,  the  closing  of  "G"  and  "F"  will,  of  course, 
open  "E"  and  "H,"  so  in  order  that  the  car  can  proceed  beyond 
these  the  lever  must  again  be  placed  normal.  The  derail  connec- 
tions are  shown  dotted.  As  an  extra  precaution  track  circuits  can 
be  installed  as  shown  on  the  steam  road,  and  the  full  normal  lever 
lock  "L"  on  the  switch  stand  will  prevent  the  conductor  from 
throwing  the  derails  should  a  train  be  within  the  limits  of  the 
track  circuits.  The  lever  lock  is  controlled  through  the  track 
relays  in  series  with  a  floor  push.  The  length  of  the  track  cir- 
cuit on  each  side  of  the  crossing  will  depend  upon  the  usual  speed 
at  which  trains  run  at  this  point,  and  as  a  rule  2,500  to  3,000  feet 
length  is  sufficient. 

Crossing  Release  Arrangements.  Where  a  separate  track 
circuit  is  not  in  service  on  either  side  of  the  crossing,  or  where 
two  ordinary  track  relays  are  employed,  a  complete  movement 
must  be  made  when  a  train  enters  one  side  of  the  crossing. 
Traffic  conditions  might  find  the  arrangement  objectionable,  as 
the  traffic  on  the  electric  road  will  be  tied  up  as  long  as  a  train 
remains  within  the  limits  of  the  track  circuit.  By  having  the  two 
relays  inter-connected  or  by  the  employment  of  a  certain  style  of 
interlocking  relay  (see  introductory  article),  as  shown  in  Fig. 
101a,  the  release  of  the  lock  will  be  accomplished  upon  the  tram 
reaching  the  crossing.  The  protection  arranged  on  the  open  cir- 
cuit principle  is  shown  in  Fig.  101b.  An  open  circuit  proposition 
is,  of  course,  always  subject  to  interruptions  of  a  serious  nature. 
Back  points  are  here  employed  and  a  lock  relay  "D"  is  necessary. 
The  train  entering  the  track  circuit  on  one  side  of  the  crossing 
will  pick  up  relay  "D"  and,  upon  reaching  the  crossing,  will  again 
drop  it,  thereby  releasing  the  lock  "L."  Any  style  of  interlocking 
relay  can  be  used  with  the  last  arrangement. 

Bolt  Lock  .Protection.  At  a  crossing  located  close  to  an 
interlocking  and  where  the  traffic  does  not  warrant  the  expense  of 

106 


ROUTE    LOCKING 

an  individual  plant,  the  derails  can  be  bolt-locked  and  the  bolt- 
locking  controlled  from  the  tower.  Thus,  the  towerman  must 
release  the  derails  before  the  conductor  can  throw  them,  which 
will  allow  each  to  test  the  veracity  of  the  other  as  to  whether  a 
train  is  approaching" ;  in  other  words,  the  responsibility  for  the 
safety  of  the  car  is  placed  on  both  men.  As  an  additional  pro- 
tection, locks  controlled  through  track  circuits  might  be  placed 
on  the  bolt  lock  lever. 

Route  Locking  Only  at  Interlockings.  By  the  employ- 
ment of  interlocked  levers  at  a  grade  crossing  more  protection 
against  improper  setting  up  of  routes  will  be  obtained.  At  a 
crossing,  as  shown  in  the  previous  figure,  a  three-lever  inter- 
locking stand  will  permit  the  conductor  to  stop  a  train  at  a  home 
signal.     Fig.  102  shows  such  an  arrangement  with  the  levers  1 


Locking 
1x3 

^x(D. 


FIG.   102. 

and  2  shown  as  being  reversed.  The  interlocking  is  arranged  so 
that  levers  1  and  2  must  be  placed  normal  before  3  can  be  re- 
versed. Furthermore,  lever  3  must  be  normal  and  lever  1 
reversed  before  lever  2  can  be  reversed.  This  accomplishes  the 
clearing  of  signal  1  and  opening  of  derail  3  before  the  conductor 
can  leave  the  stand.  Should  a  train  have  passed  the  signals,  the 
half  reverse  lock  on  the  signal  lever  will  prevent  the  lever  from 
being  placed  full  normal,  and  consequently  the  integrity  of  the 
route  is  assured  until  the  train  has  entered  the  crossing. 

Door  Lock.  There  are  grade  crossings  between  railroads 
where  the  protection  of  an  interlocking  plant  is  desired  without 
the  attention  of  a  leverman.  As  a  rule  the  traffic  of  one  road 
is  small  as  compared  with  the  other  and  the  route  is  generally 
set  for  the  road  with  heavy  traffic.  The  arrangement  is  then  to 
permit  the  trainman  to  enter  the  tower,  close  the  door,  but  before 

107 


ELECTRIC    LOCKING 


the  change  of  a  route  can  be  accomplished,  a  lever  must  first  be 
thrown,  which  operates  a  plunger  causing  the  door  to  become 
locked.  This  prevents  the  exit  of  the  trainman  until  the  original 
route  is  again  lined  up  and  the  levers  in  their  original  positions. 
The  door  locking  lever  is  generally  made  to  lock  the  signals  on 
one  road  in  the  reverse  position. 

Stick  Release  Arrangement.     A  scheme  employed  very  ex- 
tensively is  shown  in  Fig.  103.    The  train  occupying  track  section 


-?Xfe4 


FIG.   104. 

"A"  or  "B"  will  prevent  the  reversal  of  lever  2,  which  is  nor- 
mally locked.  Should  a  release  of  the  lock  be  desirable  while 
either  track  relay  is  dropped,  the  raising  of  the  knob  attached 
to  armature  of  relay  "C"  will  energize  this  relay  and  keep  the 
armature  attracted  until  the  external  circuit  is  broken  by  the 
reversal  of  lever  2.  The  lock  is  energized  in  series  with  stick 
relay  "C"  and  its  coils  will  necessarily  be  of  a  higher  resistance 
than  the  coils  of  the  relay.  (Lock  resistance  30  to  100  ohms  and 
relay  9  to  20  ohms  generally  proves  a  good  combination.)  The 
employment  of  relay  "C,"  as  shown,  is  in  the  place  of  a  time  re- 
lease, and  was  much  in  vogue  in  the  early  days  of  electric  locking. 
A  drawback  is  the  unsatisfactory  operation  of  the  lever  lock  or 
locks  (a  number  of  locks  can  be  placed  in  series)  when  in  series 
with  the  relay,  and  also  the  quick  release  of  the  route  locking, 
which  tends  to  encourage  hasty  action  on  the  part  of  the  oper- 
ator. Fig.  104  shows  a  more  elaborate  arrangement.  Signal 
lever  2  is  equipped  with  a  full  normal  and  half  reverse  lock.  The 
lock  is  controlled  through  the  track  relay  on  one  side  of  the 
crossing  only,  for  the  reason  that  as  soon  as  the  train  has  passed 
the  crossing  the  conflicting  route  might  be  cleared.  The  half 
reverse  part  of  the  lock  will  permit  the  lever  being  placed  normal 
so  as  to  put  the  signal  to  danger  after  a  train  has  passed  it,  but 

108 


ROUTE    LOCKING 

to  prevent  the  lever  from  being'  placed  full  normal,  which  would 
release  the  conflicting  route.  Stick  relay  "C"  is  employed  should 
the  operator  for  reasons  of  interruptions  in  the  track  circuit  find 
it  necessary  to  temporarily  shunt  the  track  relay  out  of  the  lock 
circuit.  The  reversal  of  the  hand  release  "D"  will  pick  up  stick 
relay  "C,"  which  will  remain  energized  provided  lever  2  is  placed 
in  the  normal  latching  position.  To  make  the  placing  of  the  re- 
lease normal  obligatory,  the  lock  is  controlled  through  a  normally 
closed  contact  on  the  release.  As  the  lock  is  also  a  full  normal 
lock,  it  is  evident  that  the  lever  cannot  again  be  reversed  unless 
the  release  is  placed  normal.  The  stick  relay  pick-up  wire  is 
broken  through  a  lever  contact  closed  while  the  lever  is  in  the 
normal  latching  position.  The  latter  arrangement  is  necessary 
in  all  cases  where  a  stick  relay  is  employed  for  emergency  re- 
lease purposes  so  as  to  compel  the  leverman  to  place  the  signal  at 
danger  before  he  attempts  to  release  the  route  by  the  use  of  the 
hand  screw  release,  and  also  to  drop  the  releasing  stick  relay  so  as 
to  restore  the  plant  to  normal  operating  conditions  as  soon  as  the 
release  is  accomplished.  If  this  was  not  arranged  it  would  result 
in  the  stick  relay  being  permanently  energized.  It  is  to  be  noted 
that  one  stick  relay  can  serve  the  purpose  for  signals  2  and  5  by 
having  the  stick-up  wire  broken  through  levers  2  and  5  in  series. 
It  is  important  that  these  contacts  be  placed  in  series,  because 
levers  2  and  5  must  be  in  the  normal  latching  position  at  one  time 
in  order  to  pick  up  the  stick  relay  and  release  the  route.  It 
should  be  noted  that  in  the  present  track  layout  lever  2  does  not 
lock  lever  5  normal,  as  both  signals  are  normally  at  clear. 

Where  Track  Circuits  Are  Objectionable.  In  most  cases 
where  an  electric  road  crosses  a  steam  road  and  where  crossing 
protection  is  desired,  the  track  circuit,  if  the  protection  proposed 
demands  one,  is  always  located  on  the  steam  road  because  these 
roads  in  most  cases  have  right-of-way  preference.  There  are 
places,  however,  where  the  electric  road  has  this  preference  and, 
as  the  rails  are  employed  for  the  propulsion  current,  the  track 
circuit  must  necessarily  be  of  an  alternating  current  type,  and 
the  expense  of  installing  a  couple  of  short"  track  sections  would 
be  prohibitive.  Fig.  105  shows  a  simple  solution  of  this  problem. 
The  trolley  wire  or  third  rail  is  insulated  at  "A"  and  "D,"  or 
whichever   place   the    route    locking    is    desired    to    be    effective. 

109 


ELECTRIC   L0CK1XG 


Relay  "F"  is  the  lock  relay  connected  across  the  feeder  and  trol- 
ley wire.  A  car  entering  the  insulated  section  of  trolley  wire 
will  take  current  through  relay  "F,"  which  will  pick  up.  The 
picking  up  of  this  relay  will  prevent  the  placing  of  the  signal  or 
derail  lever  lock  "L"  normal  until  the  car  is  out  of  the  section. 
To  prevent  a  too  heavy  current  to  flow  through  the  relay  a 
resistance  is  placed  in  series  and  a  jumper  in  multiple  with  it. 
The  type  and  size  of  this  resistance  will  depend  upon  the  voltage 
of  the  propulsion  current  and  whether  it  is  d.  c.  or  a.  c.  This 
circuit,  of  course,  is  obviously  susceptible  to  derangements  char- 
acteristic of  a  normally  open  circuit  scheme. 

Jjl.  D 


Trolley 
Third  /P( 


Bt-TSU 


==W 


^x 


\^ 


^; 


M.&r 


FIG.   106. 


Trap  Circuits.  The  locking  and  release  of  a  route  is  often 
accomplished  by  the  means  of  short  track  sections  or  track  instru- 
ments located  where  it  is  desired  that  the  locking  and  the  release 
take  place.  The  locking  section  might  be  located  at  the  distant 
or  home  signal  and  the  release  section  at  the  crossing  or  the 
limits  of  the  interlocking.  As  a  rule  a  stick  relay  is  employed 
as  a  locking  medium,  but  the  requirement  of  route  locking,  that 
no  route  be  locked  unless  the  route  is  accepted  by  a  train,  must 
be  adhered  to.  The  superiority  of  this  style  of  circuit  was 
claimed  in  the  early  days  of  electric  locking  on  account  of  its 
reducing  as  much  as  possible  the  number  and  length  of  track 
circuits.  As  will  be  seen  by  referring  to  Fig.  106  it  is  a  very 
simple  solution  of  a  route  locking  problem  and  is  often  used  in 
the  present  days  of  signaling  where  no  track  circuit  is  desired 
for  the  semi-automatic  control  of  the  signals.  "A"  is  the  locking 
and  "D"  the  release  section.  A  train  entering  section  "A"  will 
drop  stick  relay  "E,"  which  will  pick  up  when  the  train  enters 
onto  section  "D."  It  is  obvious  that  as  a  train,  when  entering 
-  :tion  "D."  will  release  the  locking,  the  distance  between  this 
section  and  the  crossing  should  be  longer  than  the  longest  train 

110 


ROUTE    LOCKING 

expected  to  traverse  the  route.  Should  it  be  impossible  to  locate 
the  releasing  track  section  at  a  distance  far  enough  from  the 
crossing  to  accommodate  long  trains,  the  lock  might  be  con- 
trolled through  a  front  point  of  the  track  relay,  as  shown  in 
dotted  lines.  This  insures  that  not  only  must  a  train  have 
reached  the  releasing  circuit  in  order  to  release  the  route,  but 
the  train  must  pass  entirely  out  of  it  before  the  levers  will  be 
released.  By  employing  a  track  instrument  as  a  release  medium 
this  arrangement  is  not  possible.  Particular  attention  is  called 
to  the  fact  that  with  a  trap  circuit  so  arranged  that  the  locking 
takes  place  upon  the  train  entering  a  route  and  the  releasing  after 
the  train  is  out  of  the  limits  of  the  interlocking,  complete  route 
locking  is  provided  and  no  throwing  of  switches  and  derails 
under  a  train  is  possible.  It  cannot  be  considered  as  safe  as  sec- 
tion locking  combined  with  route  locking,  because  dependence  is 
solely  placed  upon  the  integrity  of  the  stick  relay  circuit  and 
that  this  relay  will  operate  in  accordance  with  the  action  of  the 
apparatus  acting  as  a  locking  medium.  The  contact  on  signal 
lever  2  is  inserted  so  that  a  train  moving  in  a  direction  opposite 
to  the  one  governed  by  signal  2  will  not  drop  the  stick  relay  when 
entering  section  "A."  This  means,  of  course,  that  the  route 
locking  will  be  effective  only  when  the  train  enters  the  locking 
section  with  the  signal    at    clear.     By  arranging  the  circuit  as 


(W 


G 
FIG.   107. 


(a) 


-c- 


m. 


rid* 


shown  in  Fig.  107a,  where  an  interlocking  relay  of  the  style  indi- 
cated in  the  symbol  is  used,  it  is  possible  to  eliminate  the  signal 
contact  shunt.  Here,  in  addition  to  the  regular  two  front  points, 
a  back  point  "G"  is  employed,  which  will  keep  the  stick  relay 
energized  when  trains  run  in  the  opposite  direction  to  the  arrow. 
With  this  arrangement  the  stick  relay  should  be  slow  acting  so 
as  not  to  drop  during  the  time  interval  when  front  point  "F" 
breaks  and  back  point  "G"  makes.  Back  point  "G"  will  not 
influence  the  circuit  when  a  train,  running  in  the  direction  of  the 
arrow,  enters  section  "A."    Another  stick  relay  can  be  employed 

111 


ELECTRIC    LOCKIXC 

for  opposite  movements  and  the  lock  broken  in  series  through 
a  point  on  both  stick  relays.  Fig.  107b  shows  the  track  circuit 
as  arranged  with  the  locking  and  release  sections  on  both  ends 
of  the  interlocking  arranged  to  accomplish  the  route  locking 
without  the  employment  of  signal  contact  shunts.  This  is  a 
center-fed  track  circuit,  often  employed  to  good  advantage. 

Crossing  Lever.  If  a  grade  crossing  is  protected  by  an  inter- 
locking plant  and  complete  derail  and  signal  protection  provided, 
route  locking  protection  can  be  obtained  at  a  nominal  cost  by  the 
use  of  a  crossing  lever  and  certain  modifications  of  the  mechan- 
ical locking  in  the  interlocking  machine.  A  crossing  lever  is  a 
separate  lever  in  an  interlocking  machine,  so  designated  because 
the  locking  between  it  and  the  other  levers  protecting  the  cross- 
ing is  arranged  so  that  no  conflicting  routes  can  be  lined  up  and 
cleared  for  another  train  until  the  crossing  lever  is  released  by 
an  unoccupied  track  circuit  or  a  released  route.  An  example  of 
its    application    is    shown    in    Fig.    108.     With  the  mechanical 


.~r>.^>". 


Locking 
3x4 


FIG.   108. 


locking  arranged  as  shown,  a  rule  can  be  laid  down  to  cover  a 
more  complicated  layout,  viz. :  All  switch  and  derail  levers  or  F. 
P.  L.  levers  on  one  road  should  lock  the  crossing  lever  normal, 
and  all  switch  and  derail  and  F.  P.  L.  levers  on  the  other  road 
should  lock  the  crossing  lever  reversed.  By  controlling  a  full 
normal  and  reverse  lock  on  the  crossing  lever  through  some  route 
locking  medium  the  levers  controlling  a  movement  over  the  cross- 
ing cannot  be  reversed.  Formerly  this  protection  was  very  in- 
completely obtained  by  the  means  of  crossing  bars  located  at  the 
crossing,  as  shown  in  dotted  lines.  It  is  to  be  noted  that  with 
the  use  of  a  crossing  lever  no  protection  from  the  throwing  of 
switches  or  derails  under  a  train  is  provided. 

Route  Lever.     Route  levers,  while  very  popular  in  Europe, 
have  never  become  so  in  the  United  States  until  lately,  when  it 

112 


ROUTE    LOCKING 


was  realized  that  it  often  offers  a  very  simple  solution  to  an 
otherwise  complicated  route  locking  problem.  In  Europe  it  has 
been  considered  an  essential  operating  requirement  that  an  inter- 
locking plant  should  permit  of  any  possible  route  and  combina- 
tion of  switches  being  given  so  as  to  cover  irregular  movements 
and  emergencies.  Each  route  or  movement  was  protected  by  a 
route  lever  in  addition  to  the  signal  lever.  In  the  United  States 
route  levers  proper  are  seldom  employed,  but  certain  levers  are 
functioned  as  route  levers  (often  called  a  key  lever,  master  lever 
and  occasionally  a  lock  lever).  The  advantage  of  a  route  lever 
in  connection  with  route  locking  will  be  evident  when  it  is  con- 
sidered that  by  using  one  lever  as  a  key  lever  and  so  arrange 
the  locking  that  it  will  lock  all  other  levers  in  the  route,  the  plac- 
ing of  a  lock  on  this  lever  will  make  it  unnecessary  to  equip 
the  levers  locked  by  it  witli  lever  locks.  The  lever  chosen  to 
perform  the  function  of  a  key  lever  is  generally  an  F.  P.  L.  lever, 
where  such  are  employed  ;  at  other  places  a  switch  or  preferably 
derail  lever  is  used  for  this  purpose.  It  is  not  advisable  to  use 
a  signal  lever  as  a  route  lever  because  it  is  always  possible  to 
have  a  train  proceed  under  a  hand  signal  or  caution  card,  in 
which  case  no  route  locking  would  be  provided.  The  use  of  a 
switch  or  F.  P.  L.  lever  may  often  work  a  hardship  on  the  oper- 
ator at  a  large  mechanical  interlocking  plant  for  the  reason  that 
the  lever  so  employed  will  always  have  to  be  placed  normal  be- 
fore another  line-up  can  be  made. 


FPL  10,9 


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50£ 


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Fxu.  Hffeint  Lire*  (.w.* 


20    R*u&a»e<*  7   -  9 


(t>) 


FIG.  109. 


(d) 


At  Junctions  or  Train  Assorting  Interlockings.  The 
advantage  of  the  use  of  a  route  lever  will  be  most  apparent  at  a 
junction,  of  which  a  simple  layout  is  presented  in  Fig.  109a.     On 

113 


ELECTRIC    L O CKIN G 

this  layout  a  separate  route  lever  might  he  employed  which  will 
mechanically  lock  all  the  levers  in  the  route,  or  rather  the  func- 
tions which  are  locking  other  functions.  The  signal  levers  must 
not  be  locked  by  the  route  lever,  as  it  should  be  possible  to  put 
the  signal  levers  normal  at  any  time  irrespective  of  the  position 
or  locking  of  the  route  lever.  Assuming  lever  15  employed  as  a 
route  lever,  the  locking  for  this  lever  should  be  arranged  as  in 
Fig.  109b.  All  the  signal  levers  should  lock  lever  15  reversed. 
If  a  separate  route  lever  is  objectionable  a  lever  can  be  chosen 
which  must  be  thrown  for  any  line-up  of  switches.  This  would 
be  an  F.  P.  L.  lever  and  should  either  be  lever  10  or  lever  12. 
Assuming  the  use  of  lever  10,  this  lever  should  lock  all  other 
lock  levers  normal  or  reversed,  as  shown  in  Fig.  109c.  It  is  to 
be  noted  that  in  order  to  clear  any  route  lever  10  must  first  be 
placed  normal,  and  for  a  large  interlocking  plant  this  might  be 
objectionable. 

Pros  and  Cons  About  Route  Lexers.  The  advantage  of  the 
use  of  a  separate  lever  or  an  F.  P.  L.  lever  as  a  route  lever  is 
the  reduced  number  of  lever  locks  necessary,  and  also  that  it  will 
prevent  the  operator  from  reversing  these  levers  while  the  route 
is  locked.  Should  the  lock  be  placed  on  other  levers  it  will  be 
possible  for  the  operator  to  restore  the  F.  P.  L.  lever  normal, 
which  would  leave  the  switches  and  derails  unlocked  with  per- 
haps dire  results  if  vibrations  of  passing  trains  should  cause 
them  to  partly  open  while  a  train  is  moving  over  them.  The  dis- 
advantage of  the  arrangement  is  that  the  operator,  by  the  use 
of  a  hand  signal,  can  permit  the  train  to  proceed  without  the 
reversal  of  either  the  F.  P.  L.  levers  or  the  route  levers,  thereby 
leaving  the  train  without  protection.  By  the  use  of  derail  levers 
this  disadvantage  is  not  present,  but  additional  lever  locks  are 
required.  In  the  present  layout  two  locks  will  be  necessary,  one 
on  lever  7  and  another  on  lever  9,  and  the  locking  will  be 
arranged  as  in  Fig.  109d.  A  route  lever  locking  arrangement 
is  contrary  to  a  crossing  lever,  because  a  crossing  lever  will  pro- 
tect conflicting  routes,  while  a  route  lever  will  protect  the  route 
occupied  by  the  train.  The  circuit  for  the  route  lever  lock  can 
be  designed  to  suit  local  conditions.  If  protection  is  provided 
by  the  use  of  a  trap  circuit,  as  shown  in  Fig.  106,  it  will  be  neces- 
sary to  arrange  the  locking  circuit  as  shown  in  Fig.   110a,  and 

114 


ROUTE   LOCKING 

select  the  locking  circuit  on  lever  9  and  the  pick-up  circuit  on 
lever  11.  It  is  to  be  understood  that  this  circuit  covers  move- 
ments in  one  direction  only.  The  selecting  arrangement  is  neces- 
sary so  that  a  train  standing  in  section  "C"  will  not  release  the 
route  for  a  train  movement  from  "A"  to  "B." 


n  zo 

13  ^A  I  n  i 


With  regard  to  this  circuit  it  should  be  evident  that  a  shunt 
on  the  normal  signal  lever  contact  is  in  many  cases  necessary, 
as  described  in  connection  with  Fig.  106,  so  that  the  stick  relay 
will  not  drop  with  a  train  movement  from  "B"  to  "A."  Where 
locks  on  signal  levers  are  employed  such  shunts  are  not  abso- 
lutely necessary,  as  the  dropping  of  the  stick  relay  will  not  pre- 
vent the  clearing  of  the  signals.  The  circuit  is  designed  on  the 
selective  circuit  principle,  but  it  can  also  be  arranged  on  the 
shunt  principle,  as  shown  in  Fig.  110b,  no  selection  on  switch  9 
being  necessary.  The  trap  circuits  shown  in  Figs.  106  and  110 
are  not  the  most  desirable  for  electric  locking  purposes,  but  are 
shown  because  they  more  clearly  illustrate  the  principles  involved 
in  this  discussion.  It  is  evident  that  they  may  be  substituted  to 
advantage  by  any  of  the  trap  circuits  described  in  Chapter  III. 


A*- 


B.  EI 


ii-1 — -^    I 


T/> 


II       12.       1 

Oc  _nc 


FIG.   110b. 

Emergency  Release.  Very  few  examples  have  been  given 
in  the  present  article  concerning  emergency  releases.  It  is  ob- 
vious, however,  that  the  releasing  devices  shown  are  not  the  only 
means  which  can  be  employed,  or  that  they  are  the  most  desirable 

115 


ELECTRIC   LOCK  IXC 

in  the  circuit  to  which  applied.  There  are  a  great  variety  of 
releasing  circuits  and  devices  that  might  he  used.  Where  such 
are  purely  electrical  devices  the  circuits  and  symbols  should  be 
shown  on  the  wiring  diagram  :  where  they  are  of  a  mechanical 
origin  reference  is  made  to  their  employment  on  the  dog  and 
locking  sheet.  With  a  mechanical  hand  release  the  mechanical 
unlocking  of  the  lever  lock  must  cause  the  mechanical  locking 
of  the  signal  levers  governing  over  the  route  to  be  unlocked. 
With  an  electro-mechanical  hand  release  the  arrangement  is  that 
its  reversal  will  close  a  circuit  for  the  energization  of  the  lever 
lock  to  be  released,  while  at  the  same  time  the  signal  levers  in 
the  route  are  locked  normal  mechanically.  Fig.  109d  shows  how 
reference  is  made  to  this  effect  on  the  locking  sheet,  and  Fig. 
Ilia  shows  in  condensed  form  how  the  dog  sheet  refers  to  it. 


/     ^    3   CZ)  (S   18    19   ZO 


<£j<3  en 


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EH- 1 


13 


3u 


B+  5n.  Bus  Bar  Feeder 

£3  U< „    755w 

' Bus  Bar 


la) 


lb) 


FIG.  111. 


The  cutting  of  the  electric  lock  segment  should  be  shown  in  the 
circuit  plan  and  also  the  arrangement  of  the  circuits  for  its  re- 
lease if  used  in  connection  with  an  electro-mechanical  hand 
release.  Another  arrangement  showing  the  application  of  an 
electro-mechanical  hand  release  is  illustrated  in  Fig.  111b.  Here 
the  lever  lock  is  assumed  to  be  placed  on  the  signal  lever  and,  to 
insure  a  more  positive  dog  lock,  the  shape  of  the  dog  is  made 
square.  Before  the  signal  lever  lock  is  released  the  signal  lever  is 
put  normal  to  its  indicating  position  in  order  that  the  hand  release 
may  be  reversed.  This  also  insures  that  no  switch  lever  is 
released  until  the  release  is  again  placed  normal.  The  release 
circuit  can  be  arranged  as  shown  in  Fig.  111c.  The  reversal  of 
the  release  will  close  contact  "D,"  thereby  energizing  stick  relay 
">,"*  which  will  stay  up  until  the  signal  lever  is  placed  full  normal. 
The  lever  lock  is  controlled  through  the  front  point  of  this  relay 
and  a  normal  contact  on  the  hand  release  might  be  used  to  con- 
trol the  switch  bus  bar  or  switch  lever  locks  if  employed  in 
connection  with  an  electric  interlocking. 

116 


ROUTE    LOCKIXC 


Combined  Route  and  Indication  Locking.  For  low  volt- 
age controlled  signals  at  mechanical  interlocking  plants  it  is  not 
only  advisable  but  vital  that  some  indication  locking  protection 
be  provided.  This  can  readily  be  accomplished  in  conjunction 
with  route  locking,  an  example  of  which  is  illustrated  in  Fig. 
112.  By  always  controlling  the  lever  lock  through  normally 
closed  circuit  controllers  on  the  signals  (distant,  home,  dwarf 
or  all  of  them  in  series)  indication  locking  is  provided  for  these 
signals.  The  lock  must  also  be  controlled  through  a  locking  sec- 
tion which  might  either  be  the  track  section  between  the  distant 
and  home,  or  the  home  and  crossing  (section  "B"),  or  both. 
Under  normal  operating  conditions  the  locks  in  Fig.  112  are 
controlled   through   the   circuit   controllers    1    and   2   on   signals, 


3n* 


j£ 


—m 


~U2- 


t 


z=£n^ 


^s    ^ 


FIG.   112. 


FIG.   113. 


track  relays  "A"  and  "B,"  lock  coil  "L,"  floor  push  and  a  circuit 
controller  on  the  signal  lever.  The  reason  for  the  employment 
of  a  contact  on  the  signal  lever  has  been  discussed.  If  track 
conditions  require  the  release  of  the  route,  the  reversal  of  the 
hand  release  will  energize  the  stick  relay  "E"  through  the  reverse 
contact  on  the  release.  The  stick  relay  will  remain  energized 
through  its  own  front  point,  but  before  the  lever  lock  can  be 
energized,  the  release  must  be  put  normal  again. 


Combined  Route  and  Section  Locking.  In  order  to  com- 
bine the  route  and  section  locking  (by  many  roads  considered 
as  the  only  proper  route  locking)  the  locks  must  be  controlled 
through  all  the  track  relays  in  the  route  to  be  protected.  A 
simple  scheme  of  this  kind  for  a  single  track  road  is  shown  in 
Fig.  1 13,  where  route  locking  is  provided  for  movements  in  both 
directions.  A  train  moving  in  the  direction  of  the  arrow  will, 
when  entering  onto  section  "A."  cut  current  off  the  lock  and  by 

117 


ELECTRIC   LOCKING 

equipping  one  back  point  of  the  interlocking  relay  with  bone 
insulator,  as  shown  at  "X,"  the  route  will  be  locked  until  section 
"C"  is  reached,  when  current  is  again  applied  to  the  lock.  A 
train  moving  in  the  opposite  direction  will  release  the  lock  when 
entering  section  "A."  By  breaking  wire  "D"  through  controllers 
on  the  signals  in  series  (if  desired  also  signals  on  the  intersecting 
road)  indication  locking  in  addition  to  section  and  route  locking 
will  be  provided.  It  should  be  evident  that  in  all  previous  ex- 
amples section  locking  will  be  provided  in  addition  to  the  route 
locking  by  controlling  the  lever  locks  through  the  track  relays 
in  the  route. 

Deficient  Indication  Locking.  The  impression  prevails 
that  indication  locking  is  provided  for  the  interlocking  when 
the  circuit  for  a  lever  lock  is  broken  through  signal  circuit  con- 
trollers closed  when  the  blade  is  at  0  deg.  This  is  not  true, 
because  if  a  lock  is  placed  on  a  switch  derail  or  F.  P.  L.  lever, 
while  it  is  not  possible  to  put  this  lever  normal  to  change  a  route, 
it  is  possible  to  put  one  signal  lever  normal  and  clear  an  opposing 
signal  while  the  first  signal  is  sticking  clear.  For  this  reason 
complete  indication  locking  can  only  be  provided  by  placing  the 
lock  on  the  signal  lever. 

"SS"  Circuits.  Where  "SS"  relay  circuits  are  employed  any 
combination  of  indication,  section  and  route  locking  protection 
can  be  procured  by  the  arrangement  of  the  circuits,  as  shown  in 
Fig.    114.     With  this  arrangement,  when  the   F.  P.  L.  lever  is 

FPL. 4-  3 . , 


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Devices 


FIG.    114. 


normal  the  switch  indication  protection  takes  effect,  whereas 
with  the  lever  reversed  any  type  of  route,  approach  or  stick  lock- 
ing can  be  made  effective  with  the  application  of  the  desired 
circuit.  It  will  be  noted  that  section  locking  is  in  effect  at  all 
times. 

118 


ROUTE    LOCKING 

Terminal  Route  Locking  Applications.  At  interlocking 
plants  where  complete  section  locking  protection  is  provided  a 
route  locking  problem  can  be  very  simply  solved  by  the  employ- 
ment of  half  reverse  locks  on  the  signal  levers,  which  are  con- 
trolled in  series  through  all  the  track  sections  governed  by  the 
signal.  Should  the  signal  govern  over  more  than  one  route  the 
lock  control  will  necessarily  be  selected  with  the  different  line-up 
of  switches.  Where  locks  on  the  switch  levers  are  employed 
for  route  locking  purposes  the  circuit  will  become  somewhat 
complicated  when  used  in  connection  with  an  interlocking  where 
the  routing  of  each  signal  extends  over  a  number  of  combina- 
tions of  track  sections.     Figure  115a  shows  a  simple  layout  of 


A 

o2 

nil 

^-7f~ 

-5- 

c 

70S 

lTT?4 

.     4-r- 

-^o~~ 

a!Q 

T33 
FIG.   115a. 

this  kind.    It  will  be  observed  that  in  Fig.  115b  a  selective  scheme 
is  employed  so  that  with  certain  line-up  the  switch  lever  locks 


Bt 


-k 


lu 


"S 


L^J 


c— 


■w 


FIG.   115b. 


are  controlled  through  more  than  one  track  section.  For  the 
sake  of  simplification  each  front  contact  on  a  track  relay  is  indi- 
cated with  the  letter  for  the  track  section  by  which  the  relay  is 
controlled.  For  example,  lock  7  takes  battery  through  a  front 
point  of  track  relay  "D"  when  lever  6  is  reversed,  and  when 
levers  6  and  4  are  normal  it  takes  battery  through  track  relay 
"B."  Lock  7  goes  to  common  through  front  point  on  track  re- 
lay "C."  The  cross-protection  rules  have  not  been  followed  here, 
as  a  clearer  comprehension  of  the  route  locking  principles  will 
be  obtained  with  the  circuit  simplified,  as  shown.  Should  release 
be  desired  the  scheme  described  in  the  section  locking  article 
would  have  to  be  followed.  When  a  layout  is  not  too  complex 
a  very  good  arrangement  is  possible  with  the  shunting  method. 

119 


ELECTRIC   LOCKIXG 


In  this  scheme  (Fig.  115c)  the  lever  locks  are  controlled  in  series 
through  track  relays  and  shunted  out  when  certain  switch  levers 
are  reversed,  thereby  making  the  operation  of  the  lock  independ- 
ent of  a  train  movement  over  the  sections  which  are  shunted  out. 


^-6 


73 — r 


:D- 


*-D- 


^lf 


cc 


H^— S? 


FIG.   115c. 


Taking  lock  6  as  an  example,  its  circuit  in  the  latter  scheme  can- 
not be  combined  with  circuit  for  lock  7  through  relay  "C." 

Another  simple  terminal  layout  is  shown  in  Fig.  116a.  "A," 
"B,"  "C,"  "D,"  "E,"  "F"  and  "G"  are  track  sections  within  the 
interlocking  limits.      The  locking  circuit  for  switch  3  will,  by  the 


6 

7 

S^B 

/f 

I          *■  — 

>• 

■       ^  —            • 

nf 

Tr,        a 

(a) 

E 

0 

c 

— m~* 

_a5 

U             8    Bt 

1/   Bt 

-'-f?— 

r            Bt 

(i) 

—tf-<- 

v3       , 

4j_    B-h 

-C=fcX 

Sy             Bt 

c 

-L_5_i_ 

C E- 

(C) 

0              3> 

1 ,    Bt 

"f* G 

U F  — 

c 

4,       i 

■ — c- 

5 

; 

E 

(d) 

Bt 

Bt      v7 

^ 

Bt 

FIG.    116. 

use  of  a  selective  scheme,  be  arranged  as  shown  in  Fig.  116b, 
and  by  a  shunt  scheme  as  in  116c.  Attention  will  be  called  to 
the  fact  that  the  selecting  contacts  on  lever  3  in  Fig.  116b  must 
be  adjusted  to  make  past  the  locking  point  on  both  the  normal 
and  reverse  sides  in  order  that  the  lock  may  be  energized  past 
these  points  while  changing  the  lever  from  normal  to  reverse, 
and  vice  versa,  where  lever  locks  are  employed  for  locking 

120 


ROUTE    LOCK  ISC, 

purposes.  This,  of  course,  would  apply  to  all  selecting  contacts 
where  lever  locks  are  controlled  in  a  similar  manner.  Where 
lock  relays  are  employed  the  contacts  should  make  at  the  full 
normal  and  reverse  position  of  the  lever,  for  reasons  as  given 
in  Chapter  Y.  The  normal  contact  on  lever  4,  while  not  abso- 
lutely necessary,  as  the  circuit  will  operate  practically  the  same 
without  it,  is  shown  in  order  to  more  clearly  bring"  out  the  dif- 
ference between  the  selective  scheme,  which  this  is,  and  the 
shunting  scheme  of  circuit  control  shown  in  Fig.  116c.  The  con- 
tact i.^  also  provided  since  many  railroads  find  it  advisable  to  sep- 
arate the  various  selections  when  hunting"  trouble  and  also  because 
it  is  necessary  to  employ  this  contact  if  switches  are  located  in 
Section  D  for  wires  controlling  these. 

Assuming"  signal  X  to  be  added  to  this  layout,  there  will  be 
three  routes  between  signals  1  and  8 — one  route  from  1  to  X,  one 
from  X  to  8,  and  one  from  8  to  1.  As  route  locking"  should  only 
accomplish  the  locking  of  one  route  at  a  time,  it  is  evident  that 
a  train  moving  in  the  direction  of  the  arrow  should  lock  section 
A  only  as  it  passes  signal  1  ;  sections  G,  E,  and  G  only  after  it 
passes  signal  X,  while  the  route  for  signal  1  (section  A)  is  re- 
leased after  the  train  passes  out  of  that  route.  Hence,  switch  3 
should  be  locked  only  while  section  A  is  occupied  when  a  train 
moves  in  the  direction  of  the  arrow,  but  when  trains  move  in  the 
opposite  direction  3  should  be  locked  from  the  time  a  train  enters 
the  route  until  it  has  passed  out  of  section  A.  A  stick  relay  is 
necessary,  and  the  circuit.  Fig.  116  (d),  will  be  one  way  to  solve 
the  problem.  With  lever  1  reversed,  the  stick  relay  will  remain 
energized.  The  same  applies  when  switch  4  is  reversed.  If 
switch  4  is  normal  and  a  train  enters  section  F  or  G  with  signal 
7  or  8  clear  the  stick  relay  will  drop  and  stay  de-energized  until 
the  train  passes  signal  X.  In  this  way  the  stick  relay  will  take 
care  of  the  overlap  locking  necessitated  by  the  addition  of  signal 
X.  The  lock  on  lever  3  or  the  lock  relay  for  section  A  will  break 
through  this  relay  in  addition  to  breaking  through  track  relay 
for  section  A.  The  lock  should  of  course  also  break  through  sec- 
tion B  so  as  to  provide  protection  after  a  train  has  passed  signal 
6. 

At  Power  Interlocking.      It   is  to  be  understood   that  the 
schemes  presented  can  be  used  at  power  interlockings  as  well  as 

121 


ELECTRIC    LOCK  IXC 

mechanical  plants;  that  is,  all  levers  might  be  locked  direct.  In- 
stead of  lever  locks  it  is  possible  to  interrupt  the  control  circuit 
for  switches  and  signals  while  a  train  is  occupying  the  route  or 
a  conflicting  route  by  the  use  of  lock  relays.  Thus  in  Figs.  15  and 
16  the  lever  locks  might  be  substituted  with  lock  relays  through 
which  the  switch  control  circuits  are  broken,  or,  for  that  matter, 
the  bus  bar  feed  wires  proper  might  be  selected  without  the  use 
of  lock  relays.  When  arranging  the  circuits  proper  care  should 
be  taken,  as  outlined  in  "Section  Locking"  that  the  current  sup- 
ply is  not  cut  off  from  any  lock  relay  or  bus  bar  while  manipulat- 
ing a  lever  through  which  the  route  locking  is  selected.  There 
being  no  F.  P.  L.  levers  at  a  power  plant  the  possibility  of  obtain- 
ing route  locking  through  the  medium  of  these  levers  is  elimi- 
nated. In  some  systems  it  is  possible  to  break  the  indicating 
circuits  or  indication  wire  through  the  relays  which  are  em- 
ployed for  locking  purposes.  If  the  indication  circuit  is  broken 
it  is  evident  that  the  lever  controlled  is  locked  in  an  intermediate 
position  and  the  integrity  of  the  route  assured.  There  are  elec- 
tric interlocking  systems'  where  the  breaking  of  .the  indication 
wire  is  not  possible.  This  will  be  apparent  when  consulting  the 
indication  locking  schemes  previously  discussed  in  this  series. 

Rules  with  Regard  to  Lever  Locks.  In  addition  to  what 
was  related  under  "Section  Locking"  the  following  may  be  said 
with  reference  to  the  application  of  -lever  locks  and  their  advan- 
tages and  disadvantages  in  all  styles  of  electric  locking.  When 
route  locking  is  desired  for  the  route  occupied  the  lock,  if  placed 
on  the  signal  lever,  should  be  a  half  reverse  lock,  which  permits 
the  placing  of  the  level  normal  as  far  as  to  the  indicating  position 
but  not  the  complete  release  of  the  lever.  The  advantage  is  that 
only  one  lock  is  required  per  route,  and  the  disadvantage  that 
route  locking  is  not  provided  except  by  a  train  movement  under 
a  clear  signal.  The  lock,  if  placed  on  an  F.  P.  L.  lever  should 
be  a  full  reverse  lock.  This  arrangement  will  also  reduce  the 
number  of  lever  locks  at  a  plant  but  is  subject  to  the  objection 
just  related,  as  by  means  of  a  hand  signal  the  train  might  be  given 
the  right-of-way  without  the  reversal  of  the  F.  P.  L.  lever.  Locks 
on  derail  levers  should  be  full  reverse  and  locks  on  switch  levers 
full  normal  and  full  reverse.  As  no  route  can  be  set  up  without 
the  manipulation  of  derails  and  switch  levers  it  is  the  most  re- 

122 


-  ROUTE   LOCKING 

liable  protection.  However,  it  will  not  protect  against  the  plac- 
ing of  an  F.  P.  L.  lever  normal,  which  will  cause  the  unlocking 
of  the  switches  and  derails  while  a  train  is  occupying  the  route. 
At  places  where  the  conflicting  routes  only  are  locked  a  full 
normal  lock  on  the  signal  lever  will  protect  against  the  clearing 
of  the  signal.  A  full  normal  lock  on  the  F.  P.  L.  lock  lever  will 
prevent  the  reversal  of  this  lever,  but  in  both  cases  no  protection 
is  given  against  train  movements  under  a  hand  signal.  A  full 
normal  lock  dh  the  derail  lever. will  give  absolute  protection. 
Since  the  derails  and  the  switches  are  situated  on  the  conflicting 
route,  the  objections  just  related  regarding  the  unlocking  of  the 
switches  and  derails  where  the  route  locking  is  applied  to  the 
route  occupied  by  a  train  do  not  obtain  here.  Complete  indica- 
tion locking  is  not  possible  without  the  locks  being  placed  on  the 
signal  levers  and  complete  section  locking  onh  with  the  use  of 
locks  on  the  switches  and  derail  levers  or  where  a  switch  or  de- 
rail lever  is  employed  as  a  route  lever. 

Con'CLUsion.  A  circuit  designer  should  always  bear  in  mind 
that  when  designing  a  route  locking  circuit  the  most  complete 
protection  obtainable  should  be  provided  with  the  simplest  and, 
consequently,  most  economical  wiring  arrangement.  In  the 
various  schemes  presented  herein  it  is  to  be  noted  that,  while  they 
provide  adequate  protection  to  suit  various  conditions,  they  could 
in  many  cases  be  supplanted  with  additional  protection  by  very 
little  additional  wiring  and  thereby  provide  protection  which  will 
greatly  benefit  the  safe  operation  of  the  interlocking.  In  other 
words,  plain  route  locking  can  readily  be  arranged  in  combina- 
tion with  other  styles  of  electric  locking  so  as  to  provide  more 
complete  protection  at  a  small  additional  expense. 


123 


VII 

STICK   LOCKING 

Definition.  Stick  locking  is  defined  by  the  Railway  Signal 
Association  as  being:  "Electric  locking  taking  effect  upon  the 
setting  of  a  signal  for  a  train  to  proceed,  released  by  a  passing 
train  and  adapted  to  prevent  the  manipulation  of  levers  that 
would  endanger  an  approaching  train."  In  other  words,  stick 
locking  is  so  designed  that  the  setting  of  the  signal  will  cause  the 
locking  of  the  route  to  take  effect.  It  derives  its  name  from  the 
manner  in  which  the  locking  is  effected  and  also  because  a  stick 
relay  is  usually  an  element  of  this  style  of  locking. 

Inception  of  Stick  Locking.  In  "Section  Locking"  various 
reasons  were  set  forth  why  many  railroads  found  detector  bars 
deficient  as  a  protective  medium  and  therefore  looked  around  for 
means  whereliy  they  could  be  entirely  dispensed  with.  Track 
circuits  were  found  to  be  a  reliable  substitute  but  the  trouble 
experienced  with  slow  acting  track  relays  which  were  apt  to 
remain  energized  until  the  train  had  reached  the  first  derail  or 
switch  in  the  route  was  a  common  occurrence.  To  overcome 
this  difficulty  was  one  of  the  reasons  for  the  development  of 
stick  and  approach  locking.  Furthermore,  speed  increased  to 
such  an  extent  that  distant  signal  indications  had  to  be  given 
farther  away ;  and  as  increased  speed  means  more  space  in  which 
to  stop  it  follows  that  the  disastrous  effects  of  a  collision  or  a 
derailment  would  be  vastly  increased  should  a  clear  distant  indi- 
cation be  taken  away  from  the  engineman. 

Requirements.  1.  Stick  locking  should  be  made  effective 
(a)  with  the  clearing  of  a  signal,  or  (b)  with  the  reversal  of  the 
signal  lever  (home,  distant  or  dwarf  signal)  governing  the  route 
to  be  locked. 

2.  The  release  of  the  locking  should  be  made  effective  (a) 
with  the  restoral  of  the  lever  after  the  expiration  of  a  certain 
time  interval  and  (b)  with  the  train  having  entered  a  certain  cir- 
cuit controlling  stock  section  or  actuated  track  device. 

3.  Stick  locking  can  be  arranged  so  that  the  restoral  of  the 
signal  lever  normal  at  any  predetermined  time  is  required  before 
the   release  of  the   route   is  accomplished.     The   above   require- 

124 


STICK   LOCKING 

ments  can  be  applied  to  trains  running  in  one  direction  or  both 
directions  over  a  given  piece  of  track. 

Pros  and  Cons  About  Stick  Locking.  As  stick  locking  and 
"Approach  Locking"  are  arranged  to  provide  the  same  protec- 
tion it  might  be  well  for  comparison  to  point  out  the  advantages 
and  disadvantages  of  stick  locking.  In  stick  locking  the  disad- 
vantage lies  in  the  difficulty  of  making  signal  tests,  because 
whenever  a  sigflal  is  cleared  the  route  is  locked  and  can  only  be 
restored  to  normal  conditions  by  the  manipulation  of  the  screw 
release.  This  is  objectionable  at  a  power  plant  where  heavy 
traffic  and  perhaps  the  large  number  of  signals  will  not  permit  the 
route  to  be  tied  up  even  for  the  least  length  of  time,  and  par- 
ticularly in  places  where  the  rules  of  the  railroad  require  the 
towerman  to  test  the  movements  of  all  levers  when  coming  on 
duty.  At  a  mechanical  plant  it  will  be  annoying  particularly  in 
winter  when  it  is  necessary  to  move  the  signals  frequently  to 
keep  them  from  freezing.  At  any  plant  it  will  interfere  with  the 
flexibility  of  operation  for  the  reason  that  if  the  wrong  route  is 
lined  up  by  mistake  the  locking  of  the  route  when  no  train  has 
accepted  the  signal  will  cause  a  delay.  This  disadvantage  is  off- 
set as  approach  indicators  are  a  requirement  in  up-to-date  stick 
locking  when  applied  at  busy  interlockings  so  as  to  announce  the 
approach  of  trains  to  the  leverman  and  prevent  delays  which 
would  occur  if  the  route  was  lined  tip  and  signal  cleared  before 
a  train  was  approaching  the  distant  signal.  The  advantage  of 
stick  locking  is  the  simplicity  of  the  circuit,  as  the  locking  cir- 
cuit in  other  styles  consists  of  multiple  circuits  which  necessi- 
tates the  breaking  of  two  paths  instead  of  one  before  the  locking 
of  the  route  is  effected.  It  also  compels  deliberation  in  action 
on  the  part  of  the  leverman  before  clearing  a  signal  and  com- 
pels him  to  more  closely  attend  to  his  duties  because  a  signal 
cleared  must  also  be  accepted  by  a  train  to  effect  the  release  of 
the  route  ;  or  the  emergency  release  will  have  to  be  manipulated 
before  conflicting  routes  can  be  cleared.  This  will  prevent  the 
possibility  of  a  signal  standing  at  clear  any  length  of  time. 
Briefly,  stick  locking,  is  considered  by  many  engineers  to  promote 
discipline.  Stick  locking  is  very  popular  at  places  where  economy 
is  desired  because  only  one  track  section  or  only  one  track  in- 
strument is  necessary  for  each  route. 

125 


ELECTRIC    LOCKING 

Time  Lucks.  The  most  primitive  and  simple  way  of  applying 
stick  locking  at  an  interlocking  is  by  the  employment  of  a  time 
lock.  The  idea  of  a  time  lock  was  first  developed  with  the  desire 
of  protecting  a  derail  which,  by  reason  of  being  located  close  to 
a  signal,  could  not  be  properly  protected  by  a  track  circuit  on 
account  of  track  relays  responding  too  slowly.  It  was  also  ap- 
plied with  the  purpose  of  providing  route  locking  at  a  nominal 
cost  for  slow  speed  train  movements  without  the  use  of  a  track 
circuit  or  track  instrument  as  a  locking  and  release  medium.  It 
is  also  employed  where  the  maintenance  of  electrical  devices  are 
objectionable.  A  time  lock  is  a  mechanical  device  designed  to 
be  used  in  lieu  of  an  electric  locking  circuit.  It  will  introduce  a 
time  element  between  the  placing  of  a  signal  or  other  lever  nor- 
mal and  prevent  any  change  in  the  route  governed  by  the  signal 
upon  whose  lever  it  is  placed  until  released  by  the  lock.  The 
time  lock  will  permit  the  reversal  of  the  lever  but  it  will  prevent 
its  complete  normal  release  until  the  expiration  of  a  predeter- 
mined time  interval.  The  time  lock  will  accomplish  three  things : 
(1)  If  a  route  is  not  accepted  by  a  train  it  will  compel  the 
operator  to  use  deliberation  before  changing  the  route;  (2)  if  a 
route  is  accepted  by  a  train  it  will  prevent  the  throwing  of  a  de- 
rail or  switch  in  the  face  of  a  train,  and  (3)  it  will  prevent  the 
immediate  change  of  a  route  after  a  clear  distant  signal  is  ac- 
cepted by  the  engineman.  In  the  latter  case  it  will  be  obvious 
that  if  a  train  requires  30  seconds  to  run  between  the  distant  and 
home  signals  the  time  lock  adjusted  to  release  on  this  time  or 
longer  after  it  is  placed  normal,  will  prevent  the  change  of  the 
accepted  route  until  the  lever  is  released.  The  time  lock  has 
the  same  characteristics  as  a  half  reverse  lock,  namely,  the  lever 
is  free  to  be  placed  in  the'  normal  indicating  position  but  cannot 
be  placed  full  normal. 

The  time  lock  when  applied  to  a  slow  speed  signal  lever  for 
route  locking  protection  only  and  not  for  the  approach  protection 
of  high  speed  trains,  must  have  the  time  interval  necessary  for 
its  operation  so  adjusted  that  its  length  will  provide  the  desired 
safety  to  train  movements,  but  no  longer  than  absolutely  neces- 
sary so  as  to  result  in  decreasing  the  capacity  of  the  road. 
Should,  for  instance,  the  leverman  make  a  mistake  and  line  up  the 
wrong  route,  in  all  probability  the  waiting  train  will  be  delayed 
during   the    time    the    locking   is    being    released.      In    addition, 

126 


STK  K    LOCKING 


-witching-  movements  are  likely  to  be  hindered  by  time  locking 
unless  great  care  is  used  in  its  application.  In  many  cases  it  is 
out  of  the  question  to  so  apply  it  as  not  to  interfere  with  main 
line  switching  movements. 


*V4 


^X A**-   * 


Time  release. 
•31.,  Bf 


<-TR.on  lever*4.     W 

(b)     Q 

FIG.  117. 

Time  Releases.  A  time  release  may  also  act  as  a  time  lock 
by  attaching  it  to  a  lever  in  the  interlocking  machine  so  that 
when  it  has  once  been  actuated  from  its  normal  position  by  the 
complete  or  partial  reversal  of  the  lever  it  will  not  close  an  electric 
circuit  until  a  predetermined  interval  of  time  has  elapsed.  The 
time  release  may  also  be  placed  on  the  wall  in  the  interlocking 
tower.  The  locking  is  generally  accomplished  by  a  lever  lock- 
controlled  by  the  time  release.  Referring  to  Fig.  117a,  it  will 
be  observed  that  a  time  release  is  employed  to  pick  up  stick  re- 
lay S,  which  becomes  de-energized  with  the  reversal  of  lever  1. 
In  order  to  pick  up  the  stick  relay  the  time  release  must  be  re- 
versed after  lever  1  is  put  to  the  normal  indication  position.  As 
soon  as  the  normal  contact  on  the  time  release  is  again  made,  the 
half  reverse  lock  L  on  the  signal  lever  1  will  be  released.  It  is 
to  be  noted  that  with  all  applications  of  time  releases  the  locking 
should  be  effected  with  the  partial  reversal  of  the  signal  lever. 
Time  releases,  as  well  as  time  locks,  can  of  course  be  placed  on 
crossing,  route,  F.  P.  L.,  derail  and  switch  levers  instead  of  sig- 
nal levers,  but  it  should  not  be  effective  except  upon  the  manipu- 
lation of  a  signal  or  a  route  lever. 

For  slow  speed  movement  an  arrangement  as  shown  in  Fig. 
117b  is  often  employed.  A  time  release  on  the  dwarf  signal  lever 
will  close  a  circuit  after  a  time  interval  which  will  cause  the  ener- 
gization of  the  reverse  lock  on  derail  lever  2.  In  the  latter  case 
the  time  release  is  adjusted  to  release  on  10  seconds,  although 
at  small  interlocking*  it  is  made  longer. 

127 


ELECTRIC   LOCKING 


Without  the  Employment  of  a  Stick  Relay.  Fig.  118 
shows  an  arrangement  where  stick  locking  is  accomplished  with- 
out the  use  of  a  stick  relay.  The  reversal  of  the  signal  lever  1 
will  lock  the  route  until  the  train  has  entered  onto  C  track  sec- 
tion. The  release  is  accomplished  outside  the  limits  of  the  inter- 
locking which  will  give  full  section,  route  and  stick  locking. 
Track  sections  A  or  B,  however,  can  also  be  employed  as  release 
mediums  or,  for  that  matter  all  of  them  in  multiple  if  desired  so 
as  to  give  the  leverman  more  time  in  which  to  place  the  lever 


control. 


FIG.   118. 


C   ^B    X.  , 


ILL,      ^_ 


4U  2 


? 


ElnlSI  B-h 


Bf 


X- 


ml  m^ 

IS   ?} 

FIG.   119 


i^3 


normal.  The  lock  employed  is  a  half  reverse  lock  on  the  signal 
lever.  Contrary  to  the  majority  of  electric  locking  circuits  where 
the  lock  might  be  applied  to  any  lever  desired,  in  the  present 
circuit  the  lock  cannot  be  placed  on  a  switch  or  derail  lever  be- 
cause these  levers  must  be  free  to  be  manipulated  whenever  a 
signal  is  not  cleared.  Also,  as  previously  stated,  the  stick  locking 
shall  only  take  effect  upon  the  reversal  of  a  signal  lever  or  the 
clearing  of  a  signal.  The  screw  release  is  employed  as  discussed 
in  former  articles.  To  release  the  signal  lever  in  the  first  track 
section  of  the  route  but  still  retain  the  section  locking  it  will  be 
necessary  to  employ  an  additional  lever  lock  and  place  this  on 
the  derail  lever.  An  arrangement  of  this  kind  is  shown  in  Fig. 
119.  In  this  figure  the  reversal  of  screw  release  will  release  the 
stick  locking,  but  the  section  locking  release  will  not  take  place 

128 


STICK   LOCKING 

until  the  release  is  placed  normal  again.  It  is  to  be  noted  that 
in  most  schemes  of  stick  locking  the  lever  must  be  placed  normal 
or  rather  the  release  of  the  locking  must  be  accepted  while  the 
train  is  moving  in  the  releasing  track  section.  This  is  an  ad- 
vantage where  signals  are  not  of  a  semi-automatic  type  as  it  pre- 
vents the  leverman  from  neglecting  to  place  the  signal  at  danger 
after  the  passing  of  a  train. 

Compulsory *Restoral  of  Signal  Lever.  With  any  class  of 
electric  locking  the  circuits  may  be  so  arranged  that  it  will  be 
necessary  for  the  leverman  to  restore  his  signal  levers  to  the 
normal  position  while  a  train  is  passing  between  any  two  pre- 
determined points  in  order  to  release  the  locking;  or  it  may  be 
so  arranged  that  the  locking  will  release  automatically,  whether 
the  operator  restores  the  signal  levers  or  not.  Each  method  has 
its  particular  advantages.  If  it  is  necessary  to  restore  the  signal 
levers  to  normal  at  a  certain  time  in  order  to  release  the  locking, 
the  leverman  will  have  to  be  more  attentive  to  the  work  than 
with  the  other  arrangement,  in  order  not  to  delay  following  trains 
or  trains  on  conflicting  routes.  When  automatic  control  of  the 
signals  is  not  used  this  is  the  only  practicable  method  of  com- 
pelling the  leverman  to  restore  the  signals  to  the  stop  position 
behind  each  train.  On  the  other  hand,  if  it  is  not  necessary  to 
restore  the  signal  levers  to  the  normal  position  at  a  certain  time 
in  order  to  release  the  locking,  the  leverman  will  be  more  free  to 
attend  to  other  duties  which  are  likely  to  make  demands  upon 
him,  such  as  taking  train  orders,  etc. 


Stick  Relay  and  Locks  in  Series.  An  arrangement  which 
was  used  in  the  early  days  of  signaling  and  which  was  mentioned 
in  Chapter  VI.  is  shown  in  Fig.  120.  The  reversal  of  lever  1 
will  drop  the  stick  relay  S  and  also  lock  L  on  signal  lever.     When 

129 


ELECTRIC   LOCKING 

the  train  enters  onto  track  section  A  the  stick  relay  is  picked  up 
through  the  hack  point  on  the  track  relay,  provided  lever  1  is 
placed  normal.  The  lock,  however,  will  not  pick  up  until  the 
track  relay  is  energized  on  account  of  the  low  resistance  shunt 
provided  by  this  point.  When  A  is  energized  the  lock  picks  up 
in  series  with  the  stick  relay.  The  advantage  of  this  style  of 
locking  circuit  is  that  only  one  stick  relay  is  required  for  a  num- 
ber of  signals;  a  number  of  lever  locks  can  be  placed  in  series; 
and,  by  controlling  the  stick  .relay  through  back  points  of  all  the 
track  relays  where  the  locking  is  desired  to  be  effective,  section 
locking  will  be  provided.  The  disadvantage  is  the  difficulty  in 
providing  the  proper  relative  resistance  in  the  relays  and  locks 
when  many  are  placed  in  series,  with  the  battery  in  extreme  good 
and  poor  condition.  A  hand  key  X  is  here  used  as  an  emergency 
release  medium  and  will  have  the  same  effect  as  the  dropping 
of  the  track  relay. 

Normally  Energized  Stick  Relay.  Stick'  locking  can  be 
accomplished  by  the  means  of  a  normally  energized  stick  relay, 
an  example  of  which  is  presented  in  Fig.  121.     The  clearing  of 


4- 


c 


,3  \       .ni-.    rLu 

I       "S: ^ *fc 


m4         \    J 


4t_jfc 


W1 


c 

M~z 

FIG.   121. 

signals  2  and  1  will  drop  the  stick  relay  5  which  again  will  de- 
energize  the  signal  lever  lock  L,  which  is  here  controlled  in  multi- 
ple with  relay  S.  The  stick  relay  will  pick  up  when  train  enter> 
onto  section  C  and  the  signal  placed  normal,  when  lock  L  will 
pick  up  through  lever  contacts,  stick  relay,  screw  release  and  floor 
push.  The  stick  relay  may  be  controlled  through  the  home  or  the 
distant  lever  contact  only.  The  lock  and  stick  relay  may  also  be 
controlled  as  in  Fig.  122  through  contacts  on  all  the  signals  in 
series.  The  lock  is  here  controlled  through  a  front  point  of  the 
track  rcla\   so  that  the  route  will  be  released  only  with  the  pick- 

130 


STICK    LOCKING 

ing  up  of  the  stick  relay  and  the  track  relay,  hence  affording 
section  locking.  By  substituting  the  lever  contacts  with  contacts 
controlled  by  the  signal  arms  indication  locking  will  he  provided. 
When  a  normally  open  track  circuit  is  employed  the  stick 
relay  will  pick  up  on  the  front  point  of  the  relay  and  the  lock 
will  be  controlled  through  a  hack"  point.    In  Fig.  123  an  arrange- 


H ^ 


~~ll/t     —U/5 


X 


3^ 


nu 


eg   *V»^Vp 


¥ 


FIG.    122. 

ment  for  use  at  an  electric  road  crossing  is  shown.  It  will  be 
noted  that  the  clearing  of  signal  1  will  drop  the  stick  relay 
S  and  a  train  moving  in  the  direction  of  the  arrow,  upon  enter- 
ing the  insulated  third  rail  or  trolley  wire,  section  X,  will  pick 
up  releasing  relay  A.  For  further  details  of  an  arrangement  of 
this  kind  the  reader  is  referred  to  chapter  Vf. 


■»»■» 


^ 


11 


\Q~ro/{ey_  wire,, 

^-Feeder. 
■  fRes/stance 


bm* 


13. 


IB*- 


FIG.   123. 


With  SEMI-AUTOMATIC  SIGNALS.  When  semi-automatic 
power  signals  arc  employed  it  is  customary  to  provide  indication 
locking  in  addition  to  stick  locking  and  the  stick  relay  is  con- 
trolled through  circuit  controllers  on  the  home  and  distant 
signals,  as  shown  in  Fig.  124.  By  so  doing,  the  stick  relay  will 
not  drop  with  the  reversal  of  the  signal  lever  except  when  the 

131 


ELECTRIC    LOCKING 

signal  is  cleared.  Another  advantage  is  present — the  lever  does 
not  have  to  be  placed  normal  while  the  train  is  occupying  the 
releasing  track  section.  Should  the  compulsory  restoral  of  the 
lever  be  desired  while  the  release  by  the  train  is  effected,  the 
lever  contacts  can  be  inserted  as  shown  in  dotted  lines  ;  wire  X 
coming  out. 


*£- 


TJ/*     '    U/s 


\ 


x 


3~l 


OiU     ILL 


c 


itet 


FIG.    124. 

Where  mechanically  slotted  signals  are  employed  it  is  recom- 
mended that  two  contacts  in  series  be  used  for  each  signal  lever 
when  the  restoral  of  the  lever  is  desired.  One  contact  will  be 
controlled  by  the  tail  lever  and  another  by  the  lever  latch.  The 
former  contact  is  used  to  insure  that  the  lever  is  in  the  normal 
latching  position  and  the  mechanical  operating  parts  of  the  signal 
normal;  the  latter  contact  to  insure  that  the  lever  latch  is  up 
and  the  electric  control  of  the  signal  broken.  There  are  roads 
that  find  it  advisable  to  employ  two  contacts  wherever  a  signal 
is  controlled  and  operated  from  a  mechanical  interlocking 
machine. 


4t>    X ^^ 


^vliJf 1 — * 


& 


FIG.    126. 


Normally  De-Energized  Stick  Relay.  The  use  of  a  nor- 
mally de-energized  stick  relay  will  save  current  consumption  and 
the  circuit  can  be  arranged  as  shown  in  Fig.  125.  With  the 
reversal  of  the  lever  and  the  train  in  track  section  A  the  stick 

132 


STICK    LOCKING 


relay  S  will  pick  up  through  the  back  point  of  track  relay.  The 
lever  lock  L,  being  controlled  in  series  with  the  stick  relay,  will 
pick  up  as  soon  as  the  track  relay  drops,  which  is  contrary  to 
the  action  previously  described  in  connection  with  stick  relay 
and  locks  in  series.  The  placing  of  the  lever  fully  normal  will 
again  drop  the  stick  relay. 

A  circuit  where  the  lock  is  separated  from  the  stick  relay 
circuit  is  shown  in  Fig.  126.  The  lock  can  be  controlled  through 
front  point  of  track  relay  for  section  locking  purposes.  To 
show  the  different  methods  of  release  a  knife  switch  is  here 
shown  as  an  emergency  release  medium,  and  to  prevent  hasty 
action  should  be  located  in  the  lower  story  of  the  tower. 

Attention  is  called  to  the  fact  that  where  a  normally  de-ener- 
gized stick  relay  is  employed  compulsory  restoral  of  the  signal 
lever  normal  is  not  necessary. 


FIG.   i 


Crossing  Protection.  At  crossings  between  two  railroads 
where  light  traffic  does  not  warrant  the  employment  of  a  signal- 
man in  the  interlocking  tower  stick  locking  can  be  provided,  as 
shown  in  Fig.  127.  The  signals  4  are  normally  set  clear,  as  they 
protect  road  with  the  heaviest  traffic.  For  the  sake  of  simpli- 
fication, assume  the  circuit  as  being  designed  to  protect  a  train 
moving  in  the  direction  of  the  arrow.  A  train  entering  track 
section  A  will  release  the  lock  as  soon  as  the  trainman  has  put 
signals  4  at  danger.  If  for  any  reason  the  relay  is  not  de-ener- 
gized the  slow  release  reversed  will  shunt  out  the  track  relay  back 
point.  Lock  wire  at  X  can  be  broken  through  track  relays 
located  in  advance  of  signals  4,  thereby  insuring  that  no  train 
is  approaching  the  interlocking  or  has  accepted  the  clear  signal 
in  the  conflicting  road.    This  wire  should  also  break  through  the 

133 


ELECTRIC    LOCKING 


opposing  signals  4  in  series  and  in  multiple  through  a  back 
point  of  relay  for  track  section  B.  An  arrangement  for  a  single 
track  crossing  a  two  or  more  track  railroad  is  shown  in  Fig.  128. 
This  is  designed  to  protect  the  train  by  electric  locking  also 
while  it  is  occupying  the  dead  track  section  at  the  crossing  with- 
out the  use  of  a  trap  circuit.  Only  one  stick  relay  S  is  neces- 
sary, and  the  clearing  of  either  signal  will  cause  its  de-energiza- 
tion. In  order  that  the  release  of  the  stick  locking,  with  a  train 
moving  in  the  direction  of  the  arrow,  will  not  take  place  until 


.3    B 


~Tt/f     ~U/s 


ski-.       Jl2_ 


IS  E2 


c. 


m 


Lever  lock 


"*  circuit 


FIG.   128. 


"""^      *~Tb6 


FIG.   129. 


'.e^er/ock 
circuit 


the  train  has  entered  onto  section  B.  the  release  wire  is  broken 
through  a  full  normal  contact  on  lever  15.  As  the  lever  locks 
2  and  15  are  controlled  through  the  stick  relay  it  is  evident  that 
lever  2  cannot  be  placed  full  normal  and  consequently  the  stick 
relay  with  signal  2  cleared  cannot  pick  up  in  section  A.  It 
should  also  be  apparent  that  in  this  scheme  the  locks  must  be 
applied  to  the  signal  levers.  By  controlling  the  locks  through  a 
front  point  of  the  track  relays  the  train  must  have  passed  out 
of  the  section  before  the  route  is  released.  In  Fig.  129  two 
stick  relays  are  employed  to  insure  that  the  train   passes   over 

134 


STICK    LOCKING 


the  crossing  before  the  release  of  the  stick  locking"  is  accomplished. 
Stick  relay  D  will  pick  up  when  a  train  is  on  the  crossing  by 
the  pick-up  circuit  breaking  through  both  relay  back  points  in 
series  and  the  relay  will  stay  picked  up  as  long  as  a  train  is 
occupying  either  track  section  A  or  \).  Stick  locking  relay  S 
will  pick  up  through  a  front  point  of  relay  D  and  normal  contact 
on  signal  levers.  It  cannot  stick  up  until  the  track  circuits  are 
unoccupied,  lyhen  relay  D,  of  course,  is  dropped.  The  lever  lock 
can  be  controlled  through  front  point  of  relay  S  and  back  point 
of  relay  D,  which  will  give  section  locking  in  addition  to  stick 
locking. 

At  Power  Interlockings'.  In  stick  locking  the  arrangement 
at  power  interlockings  can  be  made  as  covered  in  chapter  VI. 
Lever  locks  can  be  employed  in  a  similar  manner,  as  at  me- 
chanical plants,  and  the  indication  wire  can  also  be  controlled 


as   shown   in   Fig. 


130. 


ELL 


The   indication   for  the   signal   is   here 


FIG.   130. 


I 


Derail  bus 
Jg  feed. 

Ind.for  sig~] 

Lever  lock 


circuit 


FIG.   131 


broken  through  a  back  point  of  the  track  relay,  which  will  pre- 
vent the  unlocking  of  the  signal  lever  until  the  train  has  entered 
the  track  circuit.  The  slow  release  will  shunt  out  the  track 
relay  contact,  but  the  switch  bus  bar  feed  or  switch  lever  lock 
circuit  will  be  open  until  release  is  placed  normal.  In  place  of 
breaking  the  indication  wire  through  a  back  point  of  the  track- 
relay  the  wire  can  be  controlled  through  front  points  of  a  stick 
relay.  The  signal  indication  wire  is  also  often  selected  on  switch 
lever  contacts  so  as  to  break  through  track  relays  with  different 
line-up  of  switches.  In  a  complex  track  layout  the  selection  and 
breaking  of  the  indication  wire  through  track  relays  often  intro- 
duces complications  in  an  otherwise  simple  circuit,  and  it  will 
be  found  to  be  of  advantage  to  substitute  lever  locks. 

135 


ELECTRIC   LOCKING 

In  Manual  Block  Territory.  At  interlockings  located  in  a 
single  track  manual  blocking  system  and  where  the  conductor 
as  well  as  the  engineman  is  held  responsible  for  the  position 
of  the  signal  it  is  a  general  rule  that  in  case  the  signal  is  placed 
normal  before  the  caboose  has  passed  it,  the  conductor's  duty 
is  to  get  the  train  stopped  and  find  out  the  cause.  In  case  a 
normally  energized  stick  relay  scheme  is  employed  and  the  pick- 
up section  is  short  it  has  happened  that  the  towerman,  to  be 
sure  to  release  the  route,  has  put  the  signal  back  before  the 
caboose  has  cleared  the  signal.  To  permit  the  release  of  the 
route,  even  if  the  signal  is  left  clear  with  the  train  out  of  the 
release  section,  two  stick  relays  must  be  employed,  as  shown 
in  Fig.  131.  Stick  relay  A  will  pick  up  on  back  point  of  track 
relay  and  stick  relay  B  will  pick  up  on  front  point  of  relay 
A  when  lever  is  put  normal.  The  lever  lock  circuit  is  broken 
through  relay  B.  Relay  A  will  drop  when  lever  is  placed  full 
normal. 

Stick  and  Indication  Locking.  In  all  schemes  described  in 
this  chapter  it  is,  of  course,  possible  to  provide  indication  locking 
by  breaking  the  stick  relay  or  the  lever  lock  through  normally 
closed  circuit  controllers  on  the  signals  for  which  an  indication 
is  desired.  Where  semi-automatic  signals  are  employed  the  re- 
lease of  the  route  will  of  course  be  accomplished  automatically 
when  the  train  enters  the  track  section  without  the  compulsory 
restoral  of  the  signal  lever.  Where  mechanically  slotted  signals 
are  used  it  is  to  be  understood  that  no  indication  is  required 
because  the  mechanical  operation  of  the  signal  is  so  arranged 
that  if  the  signal  should  stick  clear  electrically  the  restoral  of 
the  lever  will  mechanically  pull  it  to  danger  position.  It  should 
be  obvious  that  the  stick  relay  should  only  break  through  the 
signals  by  which  the  locking  is  desired,  also  that  when  breaking 
a  stick  relay  control  through  a  circuit-breaker  on  the  signal 
blade  the  controller  should  break  the  relay  circuit  only  when  the 
blade  is  in  the  position  in  which  route  locking  is  desired.  Where 
a  three-position  distant  signal  is  employed  the  stick  relay  should 
only  respond  when  the  signal  goes  above  the  45°  position  and 
the  contact  should  be  arranged  to  make  between  the  0°  and  45° 
position. 

By  employing  an  indicator  as  a  stick  relay  a  visual  indication 

136 


STICK   LOCKING 

of  the  signal  arm  going  to  danger  will  be  provided  for  the  lever- 
man,  and  also,  if  anything  goes  wrong  with  the  locking  circuit 
it  will  tell  the  leverman  that  the  position  of  the  signal  has  nothing 
to  do  with  the  trouble. 

Stick  and  Section  Lockixc;.  In  order  to  provide  section 
locking  in  combination  with  stick  locking  for  a  train  move- 
ment under  a,  clear  signal  only  the  stick  relay  should  pick  up  in 
the  last  section  in  the  route  or  the  first  section  beyond  the  inter- 
locking. Also  the  lock  relay  or  lever  lock  should  be  broken 
through  the  track  relay  points  (front  points)  in  the  route,  and 
thereby  provide  full  section  locking  protection  if  the  switches 
and  derails  have  lever  locks. 


Emergency  Releases.  Whenever  a  stick  relay  is  released 
by  the  reversal  of  a  slow  release  the  lock  which  is  released  by  the 
stick  relay  should  be  broken  through  a  normal  contact  on  the 
release.  If  the  release  does  not  contain  enough  contacts  for  this 
purpose  a  relay  can  be  controlled  by  the  normal  contact  on  the 
release  and  the  lever  locks  through  a  front  point  of  this  relay. 
In  stick  locking  the  slow  release  will  of  course  always  shunt  out 
the  releasing  medium  as  the  back  point  of  the  track  relay,  a  point 
on  a  track  instrument,  or  time  release. 


The  Control  of  the  Stick  Relay.  Stick  locking  is  most 
frequently  employed  for  high  speed  routes  only  and  for  that 
reason  the  selection  of  its  control  wire  is  often  required.     An 

ILL-. 


B+  1& 


Off/ 


FIG.  132a. 


FIG.   132b. 


example  of  a  selective  dropping  arrangement  is  shown  in  Fig. 
132a.  The  stick  relay  S  will  drop  when  signal  1  is  cleared  for  a 
movement  over  switch  2  normal  while  2  reversed  will  keep  the 
stick  relay  energized. 

137 


ELECTRIC   LOCKIXG 

Where  the  compulsory  placing  of  the  signal  lever  is  desired 
before  the  route  can  be  released  the  stick  relay  stick-up  or  pick-up 
wire  should  break  through  contacts  on  the  signal  levers  closed 
only  with  the  signal  assuming  the  stop  position.  With  a  normally 
de-energized  stick  relay  scheme  the  circuits  previously  shown 
will  pick  up  stick  relay  without  the  placing  of  the  lever  normal. 
In  Fig.  132b  an  example  is  shown  where  the  lever  must  be 
placed  normal  before  the  stick  relay  is  picked  up.  Where  the 
stick  relay  is  to  be  controlled  through  circuit  controller  on  the 
home  and  distant  signals  for  two  routes  a  selection  of  the  control 
wire  is  necessary  or  else  two  stick  relays  must  be  employed. 
Where  a  stick  relay  control  is  selected  because  one  stick  relay 
is  employed  for  two  converging  routes,  the  selecting  contacts 
must  be  arranged  to  make  before  break.     Thus,  in  Fig.   133  it 


ILL 


M3  , 


d" 


^ 


fm 


jS 


FIG.   133. 


will  be  observed  that  the  controllers  on  switch  or  switch  lever 
5  must  not  break  while  being  manipulated.  In  selecting  a  pick-up 
wire  the  mentioned  precaution  does  not  apply.  One  stick  relay 
cannot  be  employed  for  two  routes  which  can  be  cleared  simul- 
taneously.    In  Fig.  134  the  stick  relay,  if  complete  section  lock- 


FIG.   134. 


ing  is  provided,  can  pick  up  in  section  A  because  lever  2  reversed 
locks  3  normal,  and  while  the  stick  locking  is  released  with  a 
train  in  A.  lever  2  is  locked  by  the  train  occupying  this  section 
and  lever  3  is  locked  by  lever  2.  With  the  train  in  section  B. 
lever  3  is  locked  by  the  section  locking.  Cross-over  3,  being  a 
trailing  point  cross-over,  need  not  break  through  stick  relay 
for  signals   1   or   16,  because  it  is  locked  by  derails    2    anil    4 

138 


STICK    LOCKING 


reversed,  and  these  derails  break  through  the  stick  relays  and 
slow  releases.  Hence,  where  section  locking"  is  employed  the 
pick-up  of  the  stick  relay  will  not  release  the  route  until  the 
train  has  passed  out  of  the  track  sections  controlling  the  lever 
locks.     In  Fig.  135  the  pick-up  wire  for  stick  relay  for  signals  1 


^6 

~~ If^ 

A 

Z 

^ 

*~U8 

J^ 

IU3 

c 

135. 

uu 

910 

FIG 

and  2  need  not  be  selected  on  lever  5,  but  stick  relay  can  pick  up 
on  track  relay  A.  The  lock  for  lever  1,  however,  will  break 
through  track  relays  A  and  B  (signal  1  governing  over  5 
normal),  and  the  lock  for  lever  2  (signal  2  governing  over  5 
reversed)  through  relays  A  and  C  in  addition  to  breaking 
through  the  stick  relay.  The  stick  relay  pick-up  wire  may  also 
be  broken  through  front  points  of  the  track  relays  within  the 
interlocking  in  series  with  the  back  point  of  the  track  relay  out- 
side the  limits  of  the  interlocking,  as  shown  in  Fig.  136.     This 


*V4 


St' 


mr 


I  [G.    136. 


■M 


will  give  positive  assurance  that  a  stick  relay  will  stay  de-ener- 
gized while  a  train  is  moving  through  the  interlocking,  and  that 
the  train  is  completely  out  of  the  route  before  the  stick  relay 
is  released.  The  stick-up  wires  should  not  be  broken  through  a 
front  point  of  the  track  relay?  except  in  special  cases,  because 
a  train  may  cause  the  dropping  of  stick  relays  which  should 
remain  energized.  A  minimum  number  of  contacts  in  the  release 
circuit  is  an  important  factor  in  the  design  of  stick  locking 
circuits,  and  so  far  as  is  practicable  these  circuits  should  be 
made  continuous  without  its  contacts  being  made  mechanically. 
The  additional  contacts  used  in  some  schemes  introduce  addi- 
tional chances  for  failures. 

139 


ELECTRIC    LOCKLXG 


Selection  of  Stick  Relay  or  Lever  Locks.     If  a  simple 
track  layout  as  in  Fig.  137a  is  to  be  provided  with  stick,  section 


M 


B 


r-*a 


■B — & 


-A- 


-a-t 


-c 


U 


1_^L 


Bi 


Iff 


H 


]_^/ 


FIG.   137b. 


IT 


V, 


•5 


3, 


C- 


FIG.   137c. 


and  route  locking  it  can  be  arranged  by  having  the  stick  relay 
pick  up  wire  selected  so  that  with  the  clearing  of  signal  1  and 
a  straight  line-up  of  switches  the  stick  relay  will  pick  up  on 
the  last  track  section  in  the  route.  That  is,  with  levers  2,  3 
and  4  normal  the  stick  relay  will  pick  up  on  back  point  of  track 
relay  C.  If  lever  3  is  reversed  it  will  pick  up  on  back  point  of 
relay  B,  etc.  In  this  case  it  will  only  be  necessary  to  control  lever 
lock  4  through  the  stick  relay  and  track  relay  C,  as  shown  in 
Fig.  137b.  If  the  stick  relay  is  arranged  to  pick  up  on  track 
relay  A  at  all  times  it  will  be  necessary  to  control  lever  lock  4 
through  all  the  track  relays  in  the  route  in  series  and  shunt  out 
of  certain  track  relays  with  different  line-up  of  switches,  as 
shown  in  Fig.  137c.  Should  route  and  stick  locking  be  desired 
the  lock  shown  in  Figs.  137b  and  c  might  be  placed  on  the  signal 
lever  and  either  one  of  the  circuits  shown  employed.  It  will  be 
noted  that  the  two  last  described  circuits  will  give  the  same 
protection,  but  at  complex  situations  one  might  be  employed  to 
better  advantage  than  the  other. 

Example  of  Elaborate  Arrangements.  In  Fig.  138,  which 
shows  an  elaborate  stick  locking  arrangement,  indication  locking 
and  section  locking  protection  are  also  provided  for.  With  a 
train  accepting  the  route  and  having  entered  track  section  A, 

140 


STICK    LOCKING 

the  stick  relay  S  will  pick  up,  provided  the  lever  is  placed 
in  the  normal  latching  position.  The  signal  lever  lock  will 
energize  when  the  train  is  out  of  section  A,  and,  by  the  placing 
of  the  lever  full  normal,  the  stick  relay  will  again  drop.  Should 
the  trainman  neglect  to  throw  his  lever  normal  until  the  train 
has  passed  out  of  .the  track  circuit  or  if  he  wishes  to  change 
the  route  before  the  train  arrives,  it  becomes  necessary  to  reverse 
the  screw  release  F.     This  will  pick  up  stick  relay,  but  in  order 


to  release  the  lever  lock,  the  release  must  again  be  placed  normal. 
In  case  of  a  failure  of  the  local  battery  or  the  track  circuit  the 
emergency  switch  E,  which  is  enclosed  in  a  locked  case  with  a 
glass  cover  and  generally  placed  downstairs  in  the  tower,  is 
introduced  to  shunt  out  the  track  relay  and  connect  the  lever 
lock  and  stick  relay  with  the  outside  battery.  The  throwing 
of  switch  E  and  screw  release  F  will  energize  stick  relay,  which 
will  stick  up  with  screw  release  restored  normal  from  battery  at 
distant  signal.  The  lock  will  be  energized  through  the  screw  re- 
lease normal,  emergency  switch  reversed  and  front  point  of  stick 
relay.  In  order  to  again  clear  the  signal  the  emergency  switch 
must  be  placed  normal,  as  the  signal  control  is  broken  through 
a  normal  contact.  It  will  be  noted  that  the  stick  relay  will 
energize  through  two  signal  lever  contacts  in  series ;  one  contact 
operated  by  a  controller  attached  to  the  tail  lever  X  and  another 
operated  by  a  controller  connected  to  the  lever  latch  Y.  The 
lever  lock  is  controlled  through  a  contact  on  the  lever  latch 
controller  closed,  while  the  latch  is.  in  the  raised  position. 

141 


ELECTRIC   LOCKING 

Application  of  Lever  Locks.  In  view  of  the  fact  that 
stick  locking  differs  from  route  locking  by  its  effecting  the 
locking  of  a  route  by  the  clearing  of  the  signal  and  the  pro- 
tection which  it  is  designed  to  give  to  an  approaching  train,  it 
is  evident  that  the  disadvantages  mentioned  in  route  locking  as 
to  the  placing  of  the  lever  lock  on  the  signal  lever  are  not 
present  in  stick  locking.  In  stick  locking  a  route  shall  be  pro- 
tected with  the  clearing  of  a  signal,  and  consequently  the  condition 
of  the  locking  of  a  route  with  a  train  movement  under  a  hand 
signal  does  not  exist.  Hence  a  half  reverse  lock  on  signal  levers 
is  most  frequently  used  in  stick  locking  and  additional  protec- 
tion section  and  route  locking  provided  by  locks  on  F.  P.  L., 
switch  and  derail  levers.  Crossing  levers  and  route  levers  can 
be  employed  to  advantage  also  in  stick  locking  by  controlling  their 
lever  locks  through  stick  relays  which  again  are  controlled  by 
the  signals.  At  plants  where  stick  locking  is  employed  for 
high  speed  movements  it  is  customary  to  provide  section  locking 
or  route  locking,  or  route  locking  only  for  slow  speed  movements, 
to  avoid  the  inconvenience  resulting  from  the  lining  up  of  wrong 
routes,  and  also  because  no  advance  signal  indication  is  given 
for  such  train  movements.  The  precaution  given  in  section 
locking  when  controlling  lock  relays  and  locks  also  obtains  in 
stick  locking  and  further  discussion  should  not  be  necessary. 


142 


VIII 

APPROACH   LOCKING 

Definition.  Approach  locking  is  given  the  following  defini- 
tion by  the  Railway  Signal  Association :  "Electric  locking  effec- 
tive while  a  train  is  approaching  a  signal  that  has  been  set  for 
it  to  proceed,  and  adapted  to  prevent  manipulation  of  levers  or 
devices  that  would  endanger  that  train."  Approach  locking,  like- 
stick  locking,  is  generally  employed  at  places  where  trains  pass 
at  high  speed,  and  is  intended  for  the  protection  of  an  approach- 
ing train.  While  stick  locking  takes  effect  upon  the  clearing  of 
the  signal,  true  approach  locking  takes  effect  only  when  a  train 
is  approaching  and  a  signal  is  clear.  Approach  locking  is  also 
sometimes  termed  "advance  locking"  and  applied  to  lock  routes 
other  than  high  speed  routes  by  effecting  the  locking  of  the  route 
before  the  train  has  actually  entered  it. 

Requirements.  Approach  locking  should  be  made  effective 
with  a  train  passing  a  predetermined  point  while  approaching 
an  interlocking  with  the  governing  signal  in  a  certain  position. 
(The  signal  should  be  at  clear  or  display  a  caution  or  proceed 
indication.) 

The  locking  should  be  effective  at  such  distance  from  the 
governing  signal  where  it  is  visible  to  the  engineman. 

Approach  locking  can  be  made  effective  with  a  train  move- 
ment in  one  or  both  directions. 

From  this  it  will  be  evident  that  approach  locking  should 
take  place  at  such  a  distance  from  the  signal  or  signals  (when 
a  distant  signal  is  employed)  governing  the  route  that  the  route 
cannot  be  changed  after  it  has  been  accepted  by  the  engineman, 
and  if  abnormal  conditions  require  that  the  signal  be  taken  away 
after  it  has  once  been  accepted,  the  interposed  time  interval 
should  be  long  enough  to  allow  the  train  to  come  to  a  full  stop 
before  the  accepted  route  is  free  to  be  changed. 

Advantages  and  Disadvantages.  The  disadvantages  peculiar 
to  stick  locking  where  the  clearing  of  a  signal  will  effect  the 
locking  of  a  route  are  not  present  in  approach  locking.  Its 
application  will  in  many  respects  complicate  or  necessitate  a  more 
expensive   installation   as  compared   with   stick   locking;   in   fact, 

143 


ELECTRIC    LOCKING 

many  roads  consider  its  employment  prohibitive  on  that  account 
and  especially  at  small  interlockings,  where  line  circuits  are 
undesirable.  Furthermore,  sole  dependence  is  placed  upon  the 
action  of  the  "approach  lock  wire"  or  the  action  of  the  approach 
indicator  for  the  actuation  of  the  locking.  It  might  be  said 
about  any  scheme  of  electric  locking  that  whatever  additional 
contacts  are  employed  will  introduce  proportionate  chances  for 
failures,  although  proper  precautions  may  be  taken  in  the  design 
to  eliminate  failures  which  might  prove  a  source  of  danger. 
Among  the  advantages  is  the  facility  with  which  a  signal  may 
be  tested  without  inconvenience,  and  the  fact  that  it  is  not  neces- 
sary for  the  operator  to  observe  the  train  in  order  to  place  the 
signal  lever  normal  while  it  is  in  the  releasing  section.  The 
latter  advantage  of  course  might  be  considered  a  disadvantage 
by  some  engineers.  Consequently,  in  approach  locking,  if  a 
mistake  is  made  in  setting  up  a  route,  and  it  is  discovered  in 
time  the  train  will  not  be  delayed,  as  an  immediate  change  of 
line-up  is  possible.  In  most  styles  of  approach  locking  means 
must  be  employed  which  will  compel  the  leverman  to  place  the 
signal  lever  normal  after  a  signal  is  passed  by  a  train  where 
"stick"  signal  control  arrangement  is  desirable.  This  is  not 
always  considered  necessary  where  stick  locking  is  employed. 

Approach  Indicator.  An  approach  indicator  is  considered 
by  many  roads  a  necessary  adjunct  in  connection  with  approach 
locking.  The  control  of  this  indicator  differs  according  to  the. 
requirements  at  the  point  where  the  approach  locking  is  applied. 
Some  roads  stipulate  the  announcement  of  trains  to  take  place 
when  the  train  is  not  less  than  one  mile  in  the  rear  of  the  distant 
signal.      Referring  to  Fig.  139a  the  indicator  might  be  controlled 

ILL-  Sl_ 


X 

Q 


~V4  \   C     2  B  A  —"J 


* 


a 


Bt 


FIG.   139a.  FIG.    139b. 


through  track  section  A  or  B  only;  through  A  and  B  in  series 
or  through  all  intervening  sections  from  signal  X  to  1,  depending 
upon  the  scheme  of  approach  locking  employed.    Where  no  auto- 

144 


APPROACH    LOCKING 


malic  block  signals  arc  employed  it  may  break  through  a  short 
track  section  or  track  instrument  located  ahead  of  the  home 
or,  where  such  arc  employed,  ahead  of  the  distant  signal.  An 
example  of  the  application  of  a  short  annunciator  track  section 
is  shown  in  Fig.  139b.  One  rail  only  is  insulated,  and  the  distance 
between  joints  is  one  or  two  rail  lengths.  A  train  bridging 
the  rails  at  this  point  will  de-energize  approach  indicator  I. 
The  approach  indicator  when  applied  in  connection  with  approach 
locking  should  always  be  normally  energized,  as  it  is  safer  to 
place  dependence  upon  the  de-energization  of  an  apparatus  than 
upon  its  energization.  In  the  subject  under  discussion  it  is  of 
utmost  importance  that  the  approach  indicator  respond  with  a 
train  in  the  advance  section,  and  it  is  safer  to  have  the  indicator 
normally  energized  and  depend  upon  its  de-energization  than 
to  have  it  normally  de-energized  and  depend  on  its  energization 
for  the  actuation  of  the  approach  locking.  Where  automatic 
block  signals  are  employed  the  approach  indicator  may  be  con- 
trolled as  in  Fig.  139c.     Here  a  train  passing  signal  A  will  place 

I  T 

Ai 


^ 


<=L* 


FIG.   140a. 


FIG.    140b. 


FIG.  141. 


the  signal  at  danger  and  break  the  control  for  indicator  I,  which 
will  drop.  A  train  passing  signal  B  will  again  pick  up  I,  because 
the  contact  on  signal  arm  A  makes  at  45°.  This  contact,  how- 
ever, may  be  arranged  to  make  at  90°  only,  and  indicator  1 
will  remain  de-energized  until  the  train  has  passed  signal  C. 

On  single  track  roads,  or  on  roads  where  traffic  in  both 
directions  over  one  track  is  the  rule  rather  than  the  exception, 
it  is  desirable  that  the  approach  indicator  be  actuated  only  when 
trains  are  approaching  the  interlocking  plant.  Where  no  auto- 
matic signals  are  employed  interlocking  relays  and  short  track 
circuit  sections,  as  in  Fig.  140,  can  be  used  to  advantage.     The 

145 


ELECTRIC   LOCKING 

approach  indicator  can  be  made  a  stick  indicator,  and  the  circuit 
so  arranged  that  its  coil  can  be  restored  to  its  normal  position 
by  the  leverman.  Approach  indicators  of  the  drop  annunciator 
type  are  often  employed  with  circuit  arrangements  as  in  Fig.  140. 
Where  automatic  signals  are  in  service  the  circuit  can  be  arranged 
as  in  Fig.  141,  in  which  the  indicator  picks  up  only  when  a 
train  enters  track  section  A  with  signal  X  in  the  90  deg.  position. 
It  is  evident  that  for  opposing  train  movements  the  signal  will 
assume  the  45  deg.  position  before  the  track  relay  will  become 
de-energized. 

Audible  Annunciator.  In  conjunction  with  the  indicator 
an  annunciator  in  the  form  of  a  bell  or  buzzer  is  generally  em- 
ployed so  as  to  afford  an  audible  as  well  as  visual  indication  of 
the  approach  of  a  train.  Since  the  expeditious  clearing  of  a  route 
and  signal  is  of  importance  where  approach  locking  is  employed, 
various  circuit  schemes  have  been  developed  to  insure  that  a 
train  is  properly  announced  when  approaching  the  interlocking. 
It  is  also  of  importance  that  proper  means  be  adopted  to  silence 
the  buzzer  or  bell  after  it  is  observed  by  the  operator  so  as  not 
that  it  will  not  be  a  nuisance.     Fig.  142a  shows  a  buzzer  ringing 

C    &r-|  c    A 

yi    Hand  swifch. 


Buzzer  Buzzer  Buzzer[^_ 

FIG.    142a.  FIG.    142b.  FIG.    142c. 

through  a  hand  switch  and  the  back  point  of  the  indicator. 
The  operator  can  in  this  scheme  reverse  the  hand  switch,  after  the 
indicator  has  dropped,  and  thereby  stop  the  buzzer.  As  soon  as 
the  indicator  picks  up  again  it  is  necessary  that  the  hand  switch 
be  placed  normal,  as  the  buzzer  will  sound  through  the  front 
point  of  the  indicator  and  the  hand  switch  reversed.  In  scheme 
Fig.  1421)  the  buzzer  will  sound  through  the  back  point  of  the 
indicator  and  lever  contact  when  lever  1  is  normal.  With  lever 
1  reversed  for  the  clearing  of  the  signal  the  silencing  of  the 
buzzer  will  be  effected.  A  more  elaborate  scheme  is  shown  in 
Fig.  142c.  The  buzzer  will  sound  through  the  back  point  of 
the  indicator  and  back  point  of  stick  relay  X,      The  depression 

146 


.  IPPROACH   LOCKING 

of  hand  key  Y  will  pick  up  the  stick  relay,  which  will  stay 
picked  up  through  its  own  point  and  silence  the  buzzer.  Should 
signal  lever  1  be  reversed  before  the  indicator  is  dropped  the 
stick  relay  will  pick  up  when  the  indicator  drops,  and  stay  picked 
up.  The  placing  of  lever  1  normal  will  again  drop  the  stick 
relay  to  its  normal  position. 

Simple  Style  of  Approach  Locking.    Approach  locking  can 
be  arranged  as  shown  in  Fig.  143.    The  approach  indicator  should 


C     ILL      B    ^—.A 


c_M  -U,  Signal 

mX-  ^  control. 

FIG.   143. 

be  controlled  in  series  through  ail  track  sections  in  advance  of 
the  home  signal  1  so  as  to  retain  the  electric  locking  until  the 
train  passes  the  home  signal.  Thus,  in  a  circuit  of  this  style  it 
is  important  that  the  indicator  remain  de-energized  as  long  as 
the  approach  locking  is  desired  to  be  effective.  Because  of  the 
fact  that  approach  locking  shall  only  provide  protection  to  a 
train  approaching  an  interlocking  it  is  evident  that  its  release 
can  occur  after  the  train  has  passed  the  home  signal,  llence  it 
is  merely  necessary  to  control  the  half  reverse  lock  L  on  the 
signal  lever  through  the  approach  indicator  I.  Before  the  train, 
however,  has  entirely  cleared  track  section  C  another  train  may 
have  entered  section  A  or  B,  thereby  keeping  the  indicator  I 
de-energized,  which  will  prevent  the  signal  lever  from  being 
placed  normal  and  consequently  keep  the  route  locked  up.  This 
is,  of  course,  undesirable  because  a  different  lineup  of  switches 
might  be  necessary  for  the  second  train.  For  this  reason  a 
shunt  wire  X  is  employed  to  shunt  out  the  indicator  in  case 
one  train  follows  another.  This  wire  can  connect  to  a  back- 
point  of  track  relay  for  section  C  or  section  D,  or  both  of 
them  in  multiple,  if  it  is  a  busy  terminal.  Screw  release  F  is 
employed  as  previously  described. 

147 


ELECTRIC   LOCKING 


With  a  Normally  De-energized  Stick  Relay.  In  Fig.  144 
the  reversal  of  the  signal  lever  and  the  dropping  of  the  approach 
indicator  I  will  pick  up  stick  relay  S,  which  will  remain  energized 
until  the  signal  lever  is  placed  full  normal  again.  The  lever  lock 
is  not  released  until  the  train  has  entered  onto  section  C,  when 
it  is  energized  through  the  back  point  of  track  relay  C.     The 

0i_    ^_ 


T  H  Signal  con  trol. 


FIG.   144. 


release  of  the  route  can  also  be  accomplished  by  the  reversal  of 
the  screwr  release,  which  will  drop  the  stick  relay  S.  With 
a  release  arrangement  of  this  style  the  contact  G  should  not 
break  until  the  screw  release  is  fully  reversed  and  H  contact 
should  break  with  the  starting  of  the  reversal  of  the  release. 
In  the  circuit  Fig.  4  it  is  only  necessary  that  the  indicator  I 
break  through  one  track  section,  because  the  picking  up  of  the 
stick  relay  will  keep  the  route  locking  effective. 

.Another  scheme  employing  a  normally  de-energized  stick  relay 
is  shown  in  Fig.  145.  Here  the  clearing  of  signal  1  and  the 
dropping  of  indicator  I  will  effect  the  approach  locking.  The 
lever  1  placed  in  the  normal  latching  position,  and  no  train 
in  the  advance  track  sections,  will  pick  up  relay  S  and  permit 
the  lever  to  be  placed  full  normal  by  the  release  of  lever  lock 
1.  The  stick  feature  of  relay  S  is  also  utilized  in  the  emergency 
release  scheme.  The  reversal  of-  screw  release  E  will  pick  up 
relay  S  which  will  stick  up  through  its  own  point.  The  placing 
of  the  screw  release  normal  will  release  the  lock.  The  placing 
of  the  lever  full  normal  will  again  drop  the  stick  relay.  In  the 
latter  scheme  it  is  obvious  that  the  indicator  must  break  through 
all  advance  track  sections  in  series. 

Normally  Fnergized  Sttck  Relay.  A  scheme  employing 
a  normally  energized  stick  relay  will  necessarily  be  on  the  order 

148 


APPROACH   LOCKING 

of  a  stick  locking  scheme,  with  the  exception  that  the  stick 
circuit  will  break  through  a  contact  on  the  approach  indicator 
in  multiple  with  the  signal  lever  contact,  as  shown  in  Fig.  146. 
The  stick  relay  S  will  only  drop  with  the  signal  lever  2  reversed 
and  the  indicator  I  dropped.  It  will  pick  up  through  a  back 
point  of  any  track  relay  within  the  limits  of  the  interlocking  or 


B 


ry_    a    DLL., 


\t 


fS 1 

1  * 


xZ 


%W 


FIG.   147. 


~^_B±_ 


through  all  in  multiple.  It  is  to  be  noted  that  in  this  scheme 
the  necessity  of  placing  the  signal  lever  normal  while  a  train 
is  in  the  pickup  section  and  another  approaching  is  apparent. 
The  indicator  needs  only  break  through  advance  track  section  A. 
Where  combined  approach  and  indication  locking  is  employed 
in  conjunction  with  a  stick  relay  the  circuit  must  be  arranged 
differently,  because  the  stick  relay  control  will  be  carried  out  to 
the  governing  signals  instead  of  through  the  lever  contacts. 
Hence,  in  Fig.  147  stick  relay  S  will  drop  when  clearing  the 
signals,  but  placing  the  signal  normal  again  will  pick  up  the 
stick  relay,  provided  no  train  is  approaching.  If  indicator  I 
is  de-energizcd  the  stick  relay  will  not  pick  up  until  the  track 
section  C  is  occupied  or  the  screw  release  is  reversed.  In  this 
scheme  it  is  necessary,  that  the  approach  indicator  be  controlled 
through  all  the  advance  track  sections  in  series.  It  will  be 
observed  that  indication  locking  is  provided,  as  the  stick  relay  will 
not  pick  up  unless  the  signals  are  fully  normal. 

Single-Track  Application.  Approach  locking  applied  to  a 
single  track  layout  may  be  arranged  by  duplicating  the  previous 
schemes,  one  for  each  direction,  and  also  as  illustrated  in  Fig.  148. 
Approach  indicator  16  is  controlled  through  track  section  E  and 
indicator   1   through  section  A.     The  stick  relay  control  is  so 

149 


ELECTRIC   LOCK  IXC 


selected  that  if  a  train  should  cause  the  dropping  of  indicator  1  by 
entering  section  A  with  signal  16  at  clear  the  stick  relay  will  not 
drop.  With  signal  1  clear  and  indicator  1  dropped  the  stick  re- 
lay will  be  de-energized  and  not  pick  up  until  the  train  has  en- 
tered the  interlocking  limits.  In  an  approach  locking  scheme 
employing  a  stick  relay  no  provisions  for  a  second  approaching 


To  track  re  toy  back  poin.  ' 


Lock  Circuit 


FIG.   148. 


train  are  necessary.  A  single  track  approach  locking  circuit  can 
also  be  arranged  as  described  in  "Route  Locking"  by  the  em- 
ployment of  interlocking  relays  having  special  points  equipped 
with  bone  insulation. 


rOlku  wire  Or  third  ra'tl^. 


rh^rz-. 


SlU      ^ 


V 


srM, 


. 


Resistance  -? 


— «JV\ 


^4 


fndication  -LU  r 


m 


signal  1.  I 


Lock 


ffcJjT  J     S/Yf  *>  Bi  Control 


n? 


Siqnal  I. 


tL 


Circuit 


FIG.    149. 


FIG.    ISO. 


At  Electric  Railway  Crossings.  At  electric  railway  cross- 
ings a  circuit  can  be  arranged  as  in  Fig.  149,  without  the  em- 
ployment of  a  track  circuit.  A  car  running  in  the  direction  of 
the  arrow  will,  upon  entering  the  insulated  trolley  wire  section 
A,  pick  up  approach  relay  B  and  if  signal  1  is  cleared  will  cause 
the  dropping  of  stick  relay  S  through  which  the  lever  lock  is 
controlled.  The  car,  after  reaching  insulated  section  C,  will  pick- 
up releasing  relay  D  and  cause  the  energization  of  stick  relay  S, 
which  will  remain  picked  up  irrespective  of  the  position  of  the 
signal  lever.  It  will  be  noted  that  the  stick  relay  will  pick  up 
even  if  another  car  is  following  the  first,  provided  the  signa1 
lever  is  placed  normal,  so  that  no  extra  release  wire  is  necessary 
for  following  car  movements. 

150 


APPROACH    LOCKING 


At  Power  Interlockings.  Approach  locking  at  power  inter- 
locking plants  can,  as  in  Route  and  Stick  Locking,  be  applied  by 
an  interruption  of  the  indication  wire.  It  can  also  be  applied  as 
described  in  the  foregoing  parts  of  the  present  article.  If  indi- 
cation is  interrupted  the  scheme  will  be  as  illustrated  in  Fig.  150: 
the  indication  wire  is  broken  through  the  approach  indicator  for 
electric  locking  purposes ;  in  multiple  through  the  track  relay 
back  point  for  following  train  release  purposes,  and  a  reverse  con- 
tact on  the  screw  release  for  emergency  release  purposes.  The  ap- 
proach indicator  must  break  through  all  the  track  sections  in  ad- 
vance of  the  home  signal. 

A  more  complicated  arrangement  is  presented  in  Fig.   151  to 


*1  Indication 
signal  J. 

FIG.    151. 


FIG.    152. 


illustrate  variances  in  approach  locking  arrangements.  In  this 
circuit  the  operator  is  restricted  so  as  not  to  clear  signal  1  unless 
a  train  is  approaching.  This  is  accomplished  by  a  stick  relay  X 
which  is  used  as  a  signal  control  relay  and  which  will  pick  up 
only,  with  no  train  in  track  section  A,  a  train  in  the  approach 
track  sections  and  the  signal  lever  full  normal.  The  reversal  of 
the  signal  lever  will  clear  the  signal  as  the  stick  relay  X  will 
stay  picked  up  through  its  own  point  which  shunts  out  normal 
contact  on  lever  1.  ruder  normal  conditions  the  approach  lock- 
ing will  he  released  by  the  placing  of  signal  lever  1  in  the  normal 
indication  position,  which  will  pick  up  stick  relay  S  and  complete 
the  indication  circuit  for  signal  1  through  the  front  point  of 
this  relay.  Under  abnormal  conditions  the  release  of  the  lock- 
ing with  the  approach  indicator  de-energized  can  be  accomplished 
by  the  reversal  of  the  screw  release  H,  which  will  pick  up  stick 

151 


ELECTRIC   LOCKING 

relay  S  by  shunting  out  the  indicator  I.  Relay  S  will  stick  up 
but  the  release  must  be  placed  normal  before  the  indication  can 
be  procured.  Stick  relay  S  will  drop  with  the  placing  of  lever 
1  full  normal.  Approach  indicator  I  must  break  through  all  ad- 
vance track  sections.  It  should  be  observed  that  by  breaking  the 
stick  relay  S  pick-up  wire  through  a  front  point  on  track  relay 
A,  section  locking  is  also  provided  in  this  circuit. 

Crossing  Protection.  Approach  locking  can  be  applied  to 
single  track  crossings  where  on  account  of  light  traffic  it  is  not 
necessary  to  have  the  constant  attention  of  a  leverman.  The 
signals  on  the  road  with  the  heaviest  traffic  are  set  normally  at 
clear  as  shown  in  Fig.  152,  and  are  in  the  present  case  signals  1. 
The  protection  is,  for  the  sake  of  clearness  and  briefness,  de- 
signed to  give  protection  for  a  train  movement  in  one  direction 
only,  that  is  from  A  to  B.  A  trainman  on  a  train  approaching 
signal  4,  must  enter  the  interlocking  tower  and  place  signal  1 
normal.  In  order  to  release  lever  1  the  signal  must  have  assumed 
stop  position,  no  train  can  have  entered  approach  section  A  and 
the  screw  release  must  be  normal.  Should  a  train  be  standing 
in  advance  of  signal  1  the  reversal  of  screw  release  and  with  re- 
lay A  de-energized  the  release  of  lever  1  will  be  effected.  The 
screw  release  should,  if  an  electro-mechanical,  lock  lever  4  normal 
to  insure  its  restoral  normal.  If  an  electric  screw  release,  the 
control  for  signal  4  should  break  through  one  of  its  normal  con- 
tacts. Wire  X  should  also  break  through  a  normal  contact  on 
the  opposing  signal  1  and  a  contact  on  track  relay  B. 

ILL         ^ 


£ 


FIG.   153. 


■  »X  |  Switch 

/ever  locks. 
FIG.  154. 


Combined  Approach  and  Section  Locking.  Approach  and 
section  locking  protection  can  be  provided  by  controlling  the 
lever  lock  in  multiple  through  a  point  of  the  indicator  and  a 

152 


APPROACH   LOCKING 

lever  contact,  and  in  series  through  the  track  relays  within  the 
interlocking-  limits.  As  in  Fig.  153  the  lock  can  be  placed  on  the 
signal  lever  and  the  pick-up  of  the  lock  in  case  of  a  second  train 
must  occur  outside  the  track  section  controlling  the  lock.  Where 
a  stick  relay  is  employed  and  the  lock  placed  on  the  signal  lever, 
section  locking  can  be  provided  by  having  the  stick  relay  pick 
up  outside  of  the  interlocking  limits.  The  section  locking  obvi- 
ously is  only  effective  with  a  signal  clear.  Locks  on  switch  and 
derail  levers  controlled  through  track  sections  will  of  course  pro- 
vide section  locking  but  should  be  applied  independently  of  the 
approach  locking  and  as  described  in  "Section  Locking." 

Combined  Approach  and  Indication  Locking.  By  con- 
trolling the  lever  lock  through  a  circuit  controller  on  the  signal, 
indication  locking  in  addition  to  approach  locking  will  be  pro- 
vided. By  controlling  the  stick  relay  as  described  in  connection 
with  Fig.  147  the  same  will  ensue.  In  Fig.  154  an  arrangement 
which  is  very  popular  at  large  plants  is  shown.  Here  an  indi- 
cator is  employed  for  each  signal.  H  is  controlled  and  indicates 
the  position  of  home  signal  2  and  1)  the  same  for  signal  1.  Thus 
by  breaking  the  control  for  lever  lock  2  through  these  indicators 
in  addition  to  the  approach  indicator  I  an  indication  will  be 
provided  for  the  signals.  The  approach  locking  will  take  effect 
when  indicator  I  is  de-energized  and  this  indicator  must  break 
through  all  the  sections  ahead  of  the  home  signal  in  series.  Screw 
release  E  will  shunt  out  the  approach  indicator  should  a  change 
of  the  route  be  necessary  with  a  train  in  the  approach  sections. 
As  switch  lever  locks  providing  section  locking  are  generally 
employed  in  an  elaborate  scheme  of  this  kind,  these  will  break 
through  the  normal  contact  on  the  release.  In  the  case  of  a 
second  train  approaching  the  plant  the  release  of  the  lever  lock 
is  selected  on  the  various  switch  levers.  The  selection  is  necessary 
so  that  a  train  moving  in  track  section  C,  while  a  route  over 
3  reversed  is  lined  up,  will  not  release  the  route  with  a  train 
approaching  the  plant. 

In  Fig.  155,  the  clearing  of  signal  1  will  drop  the  stick  relay 
S  regardless  of  the  approach  of  a  train,  but  by  restoring  the 
signal  lever  to  the  normal  latching  position  the  stick  relay  S 
will  again  pick  up,  providing  home  and  distant  signal  assumes  the 
normal  position  and  the  plant  is  restored  to  normal  operating  con- 

153 


ELECTRIC    LOCKING 


ditions.  Instead  of  taking  battery  for  the  stick-up  circuit  through 
lever  contacts,  the  circuit  could  be  arranged  as  shown  by  dotted 
line  X,  thereby  eliminating  the  contact  on  levers  1-2.  These  con- 
tacts, however,  are  employed  in  many  installations  so  as  to 
localize  the  holding  circuit  and  not  use  the  automatic  signal  bat- 
tery for  the  purpose  of  energizing  the  stick  relay.  Approach  in- 
dicator must  be  controlled  through  all  advance  sections. 

LliU        CLL 


ILL 


ttL 


~HM 


Bf 

Lock  Circuit 


Lock  circuit 


FIG.    155. 


FIG.   156. 


Emergency  Release  Arrangements.  In  addition  to  a  screw- 
release  a  stick  relay  may  be  employed  as  a  release  medium  as 
shown  in  Fig.  156.  While  lever  1  is  reversed  and  indicator  I 
de-energized  the  reversal  of  the  screw  release  will  pick  up  the 
stick  relay  S,  and  by  placing  the  screw  release  normal  the  lock 
will  be  released.  The  contact  on  the  lever  for  signal  1  can  be 
arranged  to  make  as  at  A  or  as  at  B.  It  must  be  assured  in 
either  case  that  the  contact  breaks  with  the  lever  placed  in  the 
full  normal  position.  Attention  is  called  to  the  fact  that  in  ap- 
proach locking  the  release  circuit  should  effect  the  slumping  out 
of  the  approach  locking  mediums  only.     For  example,  at  places 


ILL     ILL, 


RA. 


n/ , 


ft,.     ^       ^ 


3: 


Re /ease  circuit 


pk 


Ti 


£ 


"HI 


Brl 

7- 


Lock  circui 


wt 


3 


FIG.  157. 


FIG.  158. 


where  indication  locking  is  combined  with  approach  locking  and 
where  an  approach  indicator  is  employed,  the  release  circuit 
should  shunt  out  the  indicator  but  not  the  signal  circuit  con- 
trollers as  shown  in  Fig.  157.  Where  no  approach  indicator  is 
used  the  arrangement  Fig.  158  is  frequently  employed.  Here 
the  lock  circuit  breaks  through  the  signals  and  approach  track 

154 


APPROACH    LOCKING 


sections  while  the  release  circuit  hreaks  through  the  signals  only. 
Approach  indicators  are  often  controlled  as  in  Fig.  159,  thereby 
acting  as  a  signal  repeater  as  well  as  an  indicator.  In  this  case 
the  release  circuit  will  either  break  through  a  signal  lever  con- 
tact or  a  separate  wire  out  to  the  signal.     Another  method  of 


*£ 


FIG.  159. 


* 


B+- 


fic.  i6o. 


FIG.    161 


controlling  an  -approach  indicator  is  shown  in  Fig.  160.  Here 
the  indicator  will  drop  when  the  signal  is  at  danger  only  and  a 
train  approaching.  The  indicator  will  also  here  act  as  a  signal 
repeater  by  showing  if  a  signal  has  responded  to  a  lever  move- 
ment with  a  train  on  the  approach  circuit. 

Advance  Locking.  Advance  locking  is  very  similar  to  ap- 
proach locking  in  that  it  locks  up  a  route  before  the  route  is 
entered,  but  it  is  employed  for  slow  and  medium  speed  train 
movements  only  and  really  is  a  modification  of  route  locking  or 
rather  sectional  route  locking,  the  difference  being  that  it  is 
effective  before  the  route  is  entered.  In  Fig.  161  it  is  desirable 
to  lock  up  the  switches  and  derails  in  track  section  B,  when  the 
train  enters  section  A.  This  is  accomplished  by  controlling  lock 
3  in  series  through  track  relays  A  and  B.  A  train  moving  in  the 
opposite  direction  from  B  to  A,  should  not  keep  lock  3  de-en- 
ergized after  it  has  passed  out  of  section  B  and  onto  Section  A, 
as  this  would  tie  up  that  part  of  the  plant  as  long  as  a  train  re- 
mained in  section  A.  With  the  employment  of  stick  relay  S 
a  train  entering  section  1'.  first,  will  pick  up  this  relay  through 
the  back  point  of  track  relay  B  and  it  will  remain  energized  as 
long  as  sections  B  and  A'are  occupied.  The  front  point  of  stick 
relay  will  shunt  out  contact  on  track  relay  A  thereby  releasing 
the  lock  with  a  movement  from  B  onto  A.  It  is  to  be  noted  that 
the  lock  is  always  controlled  through  track  relay  B  so  that  sec- 
tion locking  is  provided  at  all  times.  If  switches  in  section  A 
are  to  be  protected  with  a  train  moving  from  B  to  A  the  arrange- 

155 


ELECTRIC   LOCKING 


ment  will  be  the  same  only  that  the  action  of  the  stick  relay  is 
reversed.  In  Fig.  162  the  same  is  accomplished  in  a  different 
way.  Here  the  clearing  of  signals  1  or  2  and  the  train  entering 
track  section  A  will  drop  the  stick  relay  S  and  cause  the  locking 


FIG.    162. 


Sig.locks~~pr 


FIG.   163. 


of  lever  3.  A  train  moving  in  the  opposite  direction  will  not 
drop  the  stick  relay  owing  to  the  stick  circuit  being  broken 
through  levers  1  and  2,  but  the  lock  will  be  de-energized  as  it  is 
controlled  through  track  relay  B. 

Example  of  Complete  Protection.  In  Fig.  163  the  layout 
will  necessarily  consist  of  three  track  sections  to  take  care  of  the 
section  and  route  locking.  Two  approach  indicators  are  re- 
quired so  that  the  towerman  will  know  on  which  track  the  train 
is  approaching  the  plant.  Stick  relay  S  will  act  as  an  approach 
and  indication  locking  medium  by  dropping  as  soon  as  either 
signal  1  or  2  is  clear  and  when  a  train  is  approaching  on  either 
track.  Attention  will  be  called  to  an  error  often  committed  in 
an  approach  locking  circuit  and  that  is,  wire  X,  which  is  the 
pick-up  wire  for  the  stick  relay,  is  eliminated  and  the  stick  relay 
connected  direct  to  battery  positive  through  the  approach  indi- 
cator contacts.  This  will  mean  that  the  stick  relay  and  conse- 
quently the  lever  lock  is  released  with  the  picking  up  of  the  in- 
dicators regardless  of  the  position  of  the  signals.  The  stick  relay 
S  controls  half  reverse  locks  on  the  signal  levers.  The  release 
is  accomplished  through  the  screw  release  and  back  points  of 
track  relays  A  and  B.  Route  and  section  locking  is  provided  by 
track  relays  and  stick  relay  K.  The  signal  lever  locks  will  keep 
the  route  locking  in  effect  until  the  train  has  entered  onto  section 

156 


APPROACH   LOCKING 

A  when  the  signal  lock  is  released.  Here  the  route  and  section 
locking  takes  effect  by  track  relay  A  locking  lever  lock  4  and  also 
by  dropping  relay  K,  which  again  controls  lever  lock  5.  Stick 
relay  K  is  the  locking  relay  for  track  section  B  in  that  it  will  also 
drop  if  signal  3  is  cleared  with  switch  5  reversed  and  a  train  en- 
tering track  section  C.  A  relay  similarly  controlled  will  be 
necessary  also  for  section  C  for  the  clearing  of  signal  8  with  5 
reversed. 

Application  of  Lever  Locks.  Since  the  similarity  of  stick 
locking  and  approach  locking  lies  in  the  fact  that  no  locking  shall 
be  effective  without  the  clearing  of  a  signal  it  follows  that  in 
both  styles  the  most  favorable  and  simple  arrangement  is  to 
place  half  reverse  locks  on  the  signal  levers  and'  in  many  cases, 
as  for  instance  where  no  stick  relay  is  employed,  it  is  not  possible 
to  apply  the  locks  to  any  other  levers.  As  an  example,  suppose 
a  train  in  the  approach  section  should  lock  up  a  route  where 
only  derail  and  switch  lever  locks  were  employed,  these  levers 
would  be  locked  even  if  the  signal  was  not  cleared  and  the  lever- 
man  would  be  powerless  to  line  up  routes  except  by  using  a 
screw  release.  Here  approach  locking  would  have  defeated  its 
own  purpose.  As  in  the  last  figure  discussed,  by  the  employment 
of  a  stick  relay,  approach  locking  is  provided  without  any  addi- 
tional locks  other  than  those  employed  for  indication  locking  pur- 
poses. It  will  be  evident,  however,  that  a  number  of  different 
styles  of  locking  can  be  applied  to  an  interlocking  plant  without 
combining  the  various  kinds  of  protection.  This  is  advantageous 
from  a  designer  or  maintainer's  point  of  view  because  by  separat- 
ing and  consequently  simplifying  each  circuit,  a  less  compli- 
cated, and  a  circuit  in  which  trouble  can  readily  be  located,  will 
result.  On  the  other  hand,  from  an  economical  point  of  view  an 
arrangement  as  mentioned  is  not  always  advisable. 


157 


IX 
SECTIONAL    ROUTE    LOCKING 

Definition.  Sectional  route  locking  is  the  nomenclature  sub- 
stituted by  the  Railway  Signal  Association  for  the  previously 
termed  release  route  locking,  and  is  defined  as  follows :  "Route 
locking,  so  arranged  that  a  train,  in  clearing  each  section  of  the 
route,  releases  the  locking  affecting  that  section.'' 

As  its  name  implies,  sectional  route  locking  is  an  extension 
or  further  development  of  section  locking  and  route  locking 
combined.  In  addition  to  section  locking,  route  locking  is  pro- 
vided which,  through  the  medium  of  track  circuits,  locks  all 
levers  or  sections  governing  switches  in  any  particular  route 
when  the  train  passes  the  signal  governing  that  route.  Each 
of  the  switch  levers  or  sections  is  released  as  soon  as  the 
rear  end  of  the  train  has  passed  over  the  switch  and  is  clear  of 
the  fouling  limits  of  the  switch  leads  or  passed  out  of  the  section 
in  which  the  switch  protected  is  located.  The  releasing  of 
switches  in  the  rear  of  a  train  in  the  manner  as  set  forth  permits 
of  the  maximum  number  of  train  movements  at  maximum  protec- 
tion and  the  employment  of  this  style  of  locking  is  mostly  re- 
stricted to  larger  terminals  and  yards  where  congested  traffic 
makes  the  arrangement  necessary.  Besides  the  advantage  of 
having  portions  of  a  route  released  as  a  train  passes  beyond  them 
while  leaving  those  portions  in  advance  still  locked  it  is  obvious 
that  in  this  way  the  traffic  may  safely  be  facilitated  through  large 
terminals  without  the  use  of  a  great  number  of  signal.-. 

Requirements.  1.  Sectional  route  locking  should  be  made 
effective  with  trains  running  in  one  or  both  directions  over  a 
given  piece  of  track. 

2.  The  locking  may  become  effective  with  the  train  entering 
the  first  section  of  a  route  with  a  signal  at  clear  only  or  with  a 
signal  at  clear  or  danger. 

3.  It  can  be  arranged  so  that  the  release  will  take  effect 
only  upon  the  restoral  of  the  signal  lever  normal  at  any  pre- 
determined time  or  as  the  train  is  passing  out  of  each  track 
section. 

4.  In  all  applications  of  sectional  route  locking,  section  lock- 
ing must  under  all  circumstances  be  effective. 

158 


SECTIOXAL    ROUTE    LOCKING 

Since  sectional  route  locking  in  most  cases  is  applied  to  inter- 
lockings  protecting  large,  complex  and  congested  track  layouts, 
it  follows  that  the  circuits  employed  often  become  rather  com- 
plicated when  viewed  as  a  whole.  For  this  reason  a  sectional 
route  locking  circuit  should  be  thoroughly  analyzed  and  the 
various  elements  comprising  the  protection  separated  into  its 
various  components.  With  this  in  mind,  a  circuit  providing 
sectional  route  locking  will  prove  to  be  a  more  simple  problem 
than  at  first  anticipated,  and  it  will  be  attempted  in  the  present 
article  to  separate  and  designate  each  wire  for  the  control  of 
the  various  elements  and,  where  possible,  show  the  circuits  in 
separate  diagrams. 

Various  methods  may  be  employed  to  accomplish  sectional 
route  locking,  and  to  distinguish  one  from  the  other  each  one 
will  be  designated  scheme  A,  B,  etc.  The  main  principles  of 
each  scheme  will  be  presented  by  simplified  track  layouts, 
switches  and  turnouts  being  eliminated  to  avoid  undue  complica- 
tion in  the  circuits.  In  the  schemes  first  discussed  more  detailed 
description  will  be  presented,  as  it  will  lead  to  a  clearer  concep- 
tion of  the  following  systems  of  which  less  detailed  diagrams 
will  be  shown.  It  might  be  stated  that  of  the  many  systems  to 
be  described  some  have  the  merit  of  being  original. 

SCHEME  A. 

Description.  One  of  the  principal  elements  involved  in  sec- 
tional route  locking  will  appear  quite  simple  when  referring  to 
Fig.  164,  in  which  the  locking  is  effective  in  one  direction  only. 


C B  A  -o-;/ 

_j_ 1 1 , 

•         :   \  Lock  wire    ;    8+ 

~ET  m  121 


FIG.   164. 

The  layout  selected  shows  three  track  sections  A,  B  and  C,  with 
no  switches,  the  layout  without  these  serving  the  purpose  equally 
well.  It  is  to  be  assumed,  however,  that  each  track  section  pro- 
tects one  or  more  switches,  the  control  of  the  switches  being 
protected  either  by  means  of  lock  relays  or  lever  locks.  The 
itional  route  locking  is  assumed  to  take  effect  with  a  train 

159 


ELECTRIC   LOCKING 

movement   in   the    direction   of   the   arrow   whether  a   signal   is 
cleared  or  not. 

Diagrams.  In  order  to  explain  intelligently  the  application 
of  the  different  systems  to  various  combinations  of  signals  and 
routes,  it  will  be  necessary  to  present  all  diagrams  in  a  sim- 
plified-form, in  which  the  tracks  are  represented  by  a  single 
heavy  line  and  the  track  relay  by  a  dotted  line  running  to  the 
track  section  by  which  it  is  controlled.  Contacts  on  these  relays 
are  represented  by  a  regular  relay  contact  symbol  crossing  the 
dotted  line,  which  is  the  relay  by  which  it  is  controlled. 

Lock  Wire.  Only  one  wire  is  necessary  in  the  present  system 
and,  being  utilized  in  the  control  of  the  locks,  will  be  designated 
"lock  wire."  Locks  A,  B  and  C  will  all  become  de-energized 
with  the  dropping  of  track  relay  A ;  the  dropping  of  track  relay 
B  and  picking  up  of  track  relay  A  will  keep  locks  B  and  C 
de-energized,  but  lock  A  wTill  be  released,  and  so  on.  A  train 
moving  in  the  opposite  direction  to  the  arrow  will  only  de-ener- 
gize lock  C  when  entering  track  section  C ;  de-energize  C  and  B 
when  entering  section  B ;  and  de-energize  locks  C,  B  and  A 
as  long  as  it  remains  in  track  section  A.  It  will  be  evident 
that  a  train  first  entering  track  section  A  will  lock  up  all  the 
switches  ahead  of  it  and  release  each  lock  as  it  passes  out  of  the 
section,  while  a  train  moving  in  the  opposite  direction  will  only 
lock  the  switches  as  each  section  is  entered  and  keep  all  the 
switches  in  the  rear  locked  up  until  the  train  has  completely 
passed  out  of  the  route.  The  dotted  wire  X  shows  a  continua- 
tion of  the  lock  wire  should  the  route  be  extended  beyond  the 
limits  shown. 


<r 


jSI         13 


m 


Mockwire^  . 
A     tjBt 


FIG.   165. 


Selections.  Fig.  165  shows  the  same  scheme  with  switches 
included  in  the  track  layout,  so  as  to  take  care  of  converging 
and  diverging  routes.  The  switches  in  this  and  the  following 
diagrams  are  located  with  a  view  to  covering  the  various  com- 

160 


SECTIONAL    ROUTE   LOCKING 

binations  most  likely  to  be  met  with  in  practical  track  layout 
arrangements.  No  fouling  circuits  or  other  track  circuit  details 
will  be  shown.  The  selecting  contracts  are  shown  located  oppo- 
site the  switch,  although  it  should  be  evident  that  the  contacts 
employed  are  located  on  the  levers  operating  the  switches,  as 
it  would  be  of  prohibitive  cost  to  have  the  selections  made  out- 
side of  the  tower.  The  track  relays,  where  sectional  route  lock- 
ing is  employed,  are  generally  located  in  the  tower,  or  repeaters 
controlled  by  the  track  relays  when  such  are  used. 

Lever  lock  A  gets  positive  battery  through  track  relay  A  at 
all  times.  Selections  on  switch  2  are  necessary,  because  when 
switch  2  is  normal  battery  should  feed  the  locks  ahead  through 
track  relay  A.  If  2  is  reversed  the  locks  controlled  by  track 
sections  B,  C  and  D  should  not  be  deprived  of  positive  battery,  as 
this  would  prevent  the  lining  up  of  parallel  routes.  Thus  the 
wire  marked  X  will  be  connected  with  locks  and  break  through 
track  relays  located  in  the  route  governed  by  signal  1  when 
switch  2  is  reversed.  Following  lock  wire  A  through  track 
relay  B,  this  wire  is  selected  on  switch  3.  The  reverse  contact  on 
switch  3  will  feed  through  wire  X,  the  locks  in  the  route  governed 
by  signal  1  with  switch  3  reversed  and  the  normal  contact  on 
switch  3  will  feed  lock  C  through  4  normal  and  track  relay  C. 
If  4  is  reversed  locks  C  and  D  will  get  battery  through  the  relays 
for  track  sections  on  turnout  4. 

Applications.  As  pertaining  to  scheme  A  the  following  should 
be  observed  in  its  application :  ( a )  The  lever  locks  should 
receive  energy  from  one  direction  only.  (b)  The  lock  wire 
should  be  selected  so  that  the  throwing  of  a  switch  lever  will 
not  deprive  a  lock  of  current,  (c)  All  selecting  contacts  should 
be  arranged  to  make  before  break,  (d)  There  must  be  a  sep- 
arate lever  lock  for  each  end  of  a  cross-over,  (e)  A  lever  lock 
shall  always  break  through  a  track  relay,  (f )  Lever  locks  should 
be  employed  as  a  locking  medium. 

Comments.  While  the  advantage  of  the  present  scheme  is 
its  simplicity,  the  disadvantage  lies  in  the  difficulty  of  making 
lock  wire  selections  when  lock  relays  are  employed.  If,  for 
instance,  in  Fig.  165,  the  selecting  contacts  on  switch  3  are 
made   full  normal   and   reverse  contacts,   the   reversal   of   levers 

161 


ELECTRIC    LOCK  IXC, 

$  and  4  at  the  same  time  would  momentarily  interrupt  switch  4 
control  circuit.  Should  contacts  on  lever  3  be  arranged  to  make 
hefore  break  lever  3  could  be  placed  in  the  center  position  and 
a  train  having  entered  track  section  A  would  not  lock  switch  4, 
because  lock  relay  4  would  get  current  through  lever  contacts 
3  reversed.  Another  disadvantage  is  present  at  layouts  where 
the  route  wire  overlaps  an  opposing  signal.  A  track  layout  of 
this  kind  is  shown  in  Fig.  166.     The  route  wire,  assuming  the 

jj       D      ]*~G~     B      .A&1. 
i  iii t— 


FIG.    166. 


sectional  route  locking  to  be  effective  with  a  train  running  in  the 
direction  of  the  arrow,  will  have  to  run  from  section  A  past 
signal  6  to  section  D.  By  so  doing  a  train  running  in  the  opposite 
direction  to  the  arrow  will  tie  up  the  route  between  signals  6 
and  8  when  standing  ahead  of  signal  4. 

SCHEME  B. 

Description.  This  scheme  is  similar  to  scheme  A,  the  differ- 
ence being  that  sectional  route  locking  is  effective  in  both  direc- 
tions. Fig.  4  shows  a  simplified  track  layout  to  which  a  circuit 
typical  of  scheme  B  is  applied.  In  this  scheme  stick  relays  are 
employed  for  the  selection  of  the  direction  of  traffic.  To  simplify 
applications  at  complex  layouts,  the  circuits  should  be  divided  into 
stick  wires  and  route  wires. 

Stick  Wire.  The  stick  wire  is  the  wire  which  goes  from 
battery  positive  to  K  via  signal  lever  contact  and  stick  relay 
contact.  This  wire  should  break  through  normal  contacts  on 
one  or  more  signal  levers  and  select  on  switch  levers  so  as  to 
-hunt  out  those  signal  contacts  which  would  interfere  with  the 
clearing  of  signals  in  non-conflicting  routes. 

Route  Wire.  The  route  wire  is  the  wire  between  the  stick 
relays  or  from  K  to  K.  This  wire  is  selected  on  switch  lever 
contacts  as  in  scheme  A  and  breaks  through  the  track  relays 
between  opposing  signals.  Since  each  lever  lock  in  the  present 
scheme  under  normal  conditions  receives  energy  from  two  direc- 

162 


SECTIOXAL    ROUTE    LOCKIXG 

tions,  it  follows  that  each  side  must  break  through  a  contact 
on  the  same  track  relay  for  section  locking"  protection.  Thus 
it  will  be  noted  that  each  lever  lock  is  connected  to  the  heels 
of  two  relay  contacts,  and  this  must  be  adhered  to  whenever  the 
present  scheme  is  applied  in  a  circuit.  These  contacts  must  also 
be  connected  in  series  with  the  route  wire.  Each  end  of  the 
route  wire  is  in  most  cases  broken  through  a  stick  relay,  which 
relay  again  should  be  controlled  through  contact  on  signal 
levers  on  the  opposing  signals  at  the  opposite  end  of  the  route 
to  be  protected.  It  will  be  found  that  in  cases  where  the  selec- 
tions made  will  result  in  the  route  wire  being  controlled  by  all 
the  track  circuits  in  the  route  the  route  wire  need  not  go  through 
a  stick  relay  to  battery. 


B 


"TTtf      ! 


,         A   &k 
I  i  i 


Route 


,-tfi 


ftf  w  ^ 


wire 


<T 


5      ~S   c 

B+  x*      pi] 


FIG.   167. 


Operation.  Assume  a  train  in  Fig.  167  to  run  from  signal 
1  toward  signal  8.  Signal  1  having  been  reversed  will  remove 
battery  positive  from  the  Y  stick  relay  end  of  the  circuit  and 
current  will  be  supplied  to  all  the  lever  locks  through  stick- 
relay  Z  and  lever  8  only.  When  the  train  enters  track  section 
A  the  current  is  entirely  cut  off  all  the  lever  locks  and  stick 
relay  Y  by  the  dropping  of  track  relay  A.  Stick  relay  Z,  how- 
ever, will  stick  up  through  lever  contact  8.  The  train  clearing 
track  circuit  A  will  reapply  current  to  locks  A  through  stick 
relay  Z,  while  locks  R  and  C  will  remain  de-energized  owing 
to  the  train's  presence  in  section  B.  The  same  process  will 
re-occur  for  each  section  in  sequence  a^  the  train  passes  out  of  one 
into  another.  It  will  be  evident  that  the  restoral  of  a  signal  lever 
after  the  train  has  entered  the  route  will  not  relea-e  the  route 
ahead  of  a  train  as  the  stick  relay  cannot  pick  up  again  until 
the  train  is  entirely  out  of  the  route.     The  same  operations  will 

163 


ELECTRIC   LOCKING 

take  effect  upon  a  train  moving  in  the  opposite  direction.  In 
Fig.  168  switch  lever  selections  are  included  in  a  layout  similar 
to  Fig.  165.  The  explanation  covering  the  selection  of  the  lock 
wire  in  Fig.  165  will  apply  to  the  route  wire  in  the  present  figure. 
In  the  previous  figure  only  two  contacts  on  lever  4  were  neces- 
sary, while  in  Fig.  168  three  are  employed.     It  will  be  evident 


AT 


Crfr-T? 


~M 


tJSTL=5 


FIG.   168. 


that  the  additional  contact  is  necessary  in  scheme  B  because  posi- 
tive battery  should  be  applied  to  a  route  wire  in  both  directions. 
Locks  B  and  A  will  be  fed  positive  battery  through  lever  4 
reversed,  and  locks  C  and  D  will  take  battery  through  other 
track  relays  and  stick  relay  controlled  by  lever  8  when  switch  4 
is  reversed.  In  view  of  previous  discussion,  other  parts  of  Fig. 
168  should  be  self-explanatory. 


Route 

wire 

3 

B-r 

fc 

\J 

1 

\£ 

8-r 

Hi 


31 


FIG.    169. 


Stick  Wire  Selections.  An  example  of  a  stick  wire  selec- 
tion is  shown  in  Fig.  169.  The  stick  relay  Y  will  take  care  of 
train  movements  with  signals  1  or  2  cleared.  The  relay  is  made 
to  stick  through  signal  levers  1  and  2  in  series  but  when  switch 
3  is  normal  contact  on  2  is  shunted  out.  Tn  this  way  with  lever 
3  normal  signal  2  cleared  will  not  interfere  with  stick  relay  Y 
but  will  control  other  stick  relays  through  wire  X. 

164 


SECTIONAL    ROUTE    LOCKING 

Route  Wire  Selection.  In  Fig.  170  the  stick  relays  gov- 
erning train  movements  by  signals  opposing  signals  1  and  2  are 
shown.  Here  two  stick  relays  are  necessary  to  care  for  parallel 
train  movements.  Stick  relay  Zl  will  connect  to  route  wire  W 
with  4  normal,  with  4  reversed  it  will  connect  directly  to  positive 
battery.  Stick  relay  Z2  will  connect  with  route  wire  X  when 
lever  3  is  normal,  and  with  3  reversed  and  4  normal,  will  connect 
directly  to  positive  battery;  but  with  3  and  4  reversed  will  con- 
nect with  route  wire  W  through  track  relay  A.  With  4  reversed 
stick  relay  Zl  need  not  break  through  track  relay  A  because  4  is 
a  trailing  switch  which,  when  reversed,  prevents  the  clearing  of 


fig.  iro. 


signal  1.  Whether  3  is  normal  or  reversed,  stick  relay  Z2  must 
break  through  track  relay  B  at  all  times  because  switch  3  is  a 
facing  point  switch. 

Applications.  In  addition  to  remarks  as  to  applications  of 
scheme  A  the  following  may  be  added  for  scheme  B:  (a)  A 
stick  relay  must  be  provided  at  the  outgoing  end  for  each  route. 
(A  section  of  tracks  where  trains  run  in  both  directions  is  con- 
sidered as  two  routes.)  (b)  Normally  the  lever  locks  should 
receive  energy  from  two  directions,  (c)  In  the  present  scheme 
it  will  be  to  advantage  to  designate  the  stick  relay  with  letter  S 
and  suffix  the  track  circuit  letter  or  number  of  the  end  track 
circuit. 


Comments.     While  the  application   of  scheme  B   requires  a 
limited  number  of  track  relay  and  lever  contacts,  a  disadvantage 

165 


ELECTRIC   LOCKING 

will  be  found  in  certain  track  layout  and  signal  arrangements 
when  the  circuits  will  become  very  complicated.  Also  lock  re- 
lays cannot  he  employed  for  reasons  set  forth  in  the  discussion 
of  scheme  A. 

SCHEME  C. 

Description.  In  the  present  system  one  stick  relay  only  is 
employed  for  the  signal  governing  a  movement  in  one  direction 
while  the  opposing  signal  has  no  stick  relay.  The  stick  relay  is 
normally  de-energized  and  with  the  clearing  of  one  signal  this 
relay  will  stay  down  while  the  clearing  of  the  opposing  signal 
will  energize  the  stick  relay.  The  lever  locks  are  controlled 
through  the  front  and  back  points  of  the  stick  relay  and  in  this 
manner  the  energized  or  de-energized  state  of  the  stick  relay 
will  select  the  direction  in  which  the  electric  locking  shall  be 
effective. 

The  circuits  are  divided  into  two  general  classes,  the  stick  re- 
lay circuits  and  the  lever  lock  circuits. 

Stick  Relay  Circuit.     Fig.  171  shows  the  stick  relay  circuit 


EI 


FIG.   171. 


FIG.    172. 


applied  to  a  simplified  track  layout  and  the  circuit  is  composed 
of  two  parts,  the  pick-up  wire  X  which  breaks  through  lever  8 
reversed,  and  the  stick-up  wire  Y  which  is  controlled  through 
back  points  of  all  the  track  relays  in  the  route  in  multiple.  Stick 
relay  S  will  pick  up  if  signal  8  is  cleared  and  stick  up  through  the 
stick  wire  Y  while  a  train  is  occupying  the  track  sections  in  the 
route.  With  lever  1  reversed  the  stick  relay  will  remain  de-en- 
ergized. It  will  readily  be  seen  that  restoring  one  signal  to 
normal  position  and  clearing  the  opposing  signal  will  reverse  the 
position  of  the  stick  relay  and  consequently  reverse  the  sectional 
route  locking. 

166 


SECTIONAL   ROUTE  LOCKIXG 

Lock  Circuit.  In  Fig.  172  the  lock  circuit  is  shown  as  ap- 
plied to  the  same  layout  as  in  previous  figure.  The  lock  circuits 
are  composed  of  two  parts,  namely,  the  battery  feed  wire  W  and 
the  lock  wire  Z.  The  lock  wire  receives  battery  from  a  back  con- 
tact of  the  stick  relay  while  battery  is  fed  to  the  other  end  of  the 
route  over  the  battery  feed  wire  through  the  front  point  of  re- 
lay S.  Thus,  it  will  be  seen  that  when  a  train  is  going  in  the 
direction  when  the  stick  relay  is  energized,  battery  is  fed  behind 
the  train  as  it  proceeds.  When  the  train  is  proceeding  in  the 
opposite  direction  the  stick  relay  being  de-energized,  the  current 
is  also  fed  from  behind  the  train.  The  lock  wire  from  either 
side  is  also  controlled  through  a  front  point  on  the  track  relay 
of  the  section  in  which  the  switch  is  located,  thus  providing  abso- 
lute section  locking.  It  will  be  evident  that  by  combining  the 
stick  relay  and  lock  circuits  the  switches  and  derails  will  always 
be  locked  ahead  of  and  under  a  train  while  those  behind  a  train 
will  be  unlocked. 


E^~fe^ 


FIGS.    173a  and   173b. 


Operation.  Referring  to  Figs.  71  and  72  the  operation  will 
be  as  follows :  The  reversal  of  lever  8  will  pick  up  stick  relay 
S  and  the  relay  will  stick  up  through  hack  joints  of  the  track  re- 
lays in  the  route.  The  picking  up  of  this  relay  will  cut  current 
supply  from  lock  wire  Z  and  the  locks  will  be  fed  through  bat- 
tery feed  wire  W,  through  front  point  of  stick  relay  S  and  front 
point  of  track  relay  C.  A  train  entering  track  section  C  will  de- 
energize  all  the  lever  locks,  but  a  train  having  passed  from  sec- 
tion C  onto  section  B  will  energize  lock  C,  and  so  on.    The  clear- 

167 


ELECTRIC   LOCKIXC 


ing  of  signal  1  will  feed  all  locks  through  the  back  point  of  stick 
relay  and  through  front  point  of  track  relay  A. 

Selections  of  Stick  Relay  Circuit.  In  the  track  layout  in 
Fig.  173a  the  pick-up  wire  is  selected  on  switches  2  and  3;  if 
either  one  is  reversed  the  X  wire  will  select  on  other  switches 
and  through  the  lever  contact  on  an  opposing  signal.  Wire  Y 
which  is  connected  to  reverse  contact  on  switch  4  will  go  to  a 
stick  relay  which  controls  the  route  locking  for  the  signal  oppos- 
ing signal  8  when  switch  4  is  reversed.  Stick-up  wire  is  selected 
so  as  to  connect  with  other  relay  back  points  through  wire  W 
when  2  or  3  is  reversed.  Wire  Z  is  a  pick-up  wire  for  an  oppos- 
ing route  stick  relay. 

C  B  A      m 


f"LX? 


D 

— i— 


B+ . 


at. 


!+_ 


b+  a/ 


& 


^U6 


8+ 


8t 


EI  EI 


Hi 


% 


SIS 


dC 


\*  c 


B±^ 


FIG.   174. 


FIG.   175. 

Lock  Circuit  Selections.  In  Fig.  173b  the  lock  wire  and 
battery  feed  wire  selections  are  shown.  The  battery  feed  wire  is 
selected  on  levers  2  and  3  so  as  to  feed  other  locks  through  wire 
T  if  either  one  is  reversed.  The  selection  on  lever  4  is  made  so 
that  locks  will  receive  energy  through  other  stick  relays  by  con- 
nection V.  Lock  wire  is  selected  on  levers  2  and  3  to  connect 
with  other  track  relays  by  connection  U  and  to  feed  locks  D  and 

168 


SECTIONAL    ROUTE    LOCKING 


C  when  switch  2  or  3  is  reversed.  Wire  R  will  connect  to  bat- 
tery through  other  stick  relays.  Figs.  174  and  175  show  lay- 
outs with  signals  added  to  the  diagrams.  In  Fig.  174  two  stick 
relays  are  required  and  an  overlap  lock  wire  P  is  necessary.  In 
Fig.  175  the  same  number  of  relays  are  required  and  an  overlap 
pick-up  wire  N  is  necessary.  In  view  of  previous  description 
these  figures  should  be  readily  understood. 

Applications.  "Most  of  the  previous  remarks  as  to  applica- 
tions will  also  apply  to  this  system  and  in  addition  the  follow- 
ing might  be  said:  (a)  Only  signals  governing  movements  in 
one  direction  have  stick  relays  connected  to  them,  (b)  The 
stick-up  wire  should  be  selected  through  switches  and  controlled 
through  track  relay  back  points  so  that  at  no  time  will  battery 
be  disconnected  from  the  stick  relay  while  the  train  is  occupying 
the  route  between  the  signals,  (c)  The  battery  feed  wire  and 
lock  wire  should  be  selected  so  that  with  a  different  line-up  of 
switches  the  current  is  always  applied  to  the  locks  through  either 
a  front  or  a  back  point  on  a  stick  relay. 

(  Comments.  The  only  disadvantage  in  this  scheme  is  the  de- 
pendence which  is  placed  upon  the  stick  relay  without  an  auto- 
matic check  being  made  on  its  operation.  Should  this  relay,  for 
instance,  remain  de-energized  no  sectional  route  locking  will  be 
provided  with  train  movements  in  one  direction  and  should  it 
stick  up  the  opposite  direction  will  be  without  route  locking. 

SCHEME  D. 
Description.     This  scheme  is  very  much  like  scheme  C  ex- 
cept that  in  scheme  D  the  stick  relay  is  normally  energized  and 

C  B  a  a*/ 


~ai 


j<v 


B±_ 


c  L3£)l_z_:!±£n_Z_p£] 


Fig.    176. 


only  controlled  through  one  signal.  The  wires  can  be  desig- 
nated as  in  the  previous  scheme.  W  being  the  battery  feed  wire, 
Z  the  lock  wire,  Y  the  stick-up  wire  and  X  the  pick-up  stick  re- 

169 


ELECTRIC   LOCKING 

lay  wires.  Fig.  176  shows  the  application  of  the  system.  It  will 
be  noted  that  stick  relay  S  will  drop  if  signal  1  is  cleared  but 
with  signal  8  cleared  it  will  not  drop  until  the  train  has  entered 
track  section  C  when  the  locking  will  take  effect.  Figs.  177a  and 
177b  show  the  application  and  selections  necessary  in  scheme  D 


M     EI 


FIGS.  177a  and  177b. 


a 


and,  being  so  closely  related  to  the  previous  scheme,  no  further 
comment  should  be  necessary. 


SCHEME  E. 

Description.     This  scheme  is  similar  to  the  foregoing.     Here, 

however,  one  stick  relay  is  employed  for  each  route,  or  rather 

one  for  each  signal.     In  this  way  the  objectionable  back  point 

lock  control  is  eliminated.     Figure  178  shows  the  application  of 

C  B  A 


Tr<9 


etii 


;    Pick-up  wire\  


FIG.   178. 

this  system  and  it  will  be  noted  that  a  separate  stick  and  pick- 
up wire  is  used  for  each  stick  relay,  while  only  one  lock  wire  is 
employed  which  is  connected  to  positive  battery  at  each  end  of 
the  route  through  the  stick  relay  governing  opposing  train  move- 
ments. The  clearing  of  signal  1  will  drop  stick  relay  IS  when 
a  train  enters  track  section  A  while  stick  relay  8S  will  remain 
energized.  The  dropping  of  stick  relay  IS  will  cut  off  the  cur- 
rent supply  for  the  locks  at  this  end  of  the  circuit ;  and  the  drop- 

170 


SECTIONAL    ROUTE    LOCKING 

ping  of  track  relay  A  when  the  train  enters  that  section  will  cut 
off  current  from  the  other  end,  thus  depriving  all  lever  locks 
ahead  of  the  train  with  current.  Because  locks  in  section  A  get 
current  through  front  point  of  stick  relay  8S  it  follows  that 
locks  A  will  be  released  as  soon  as  a  train  is  out  of  Section  A. 

Applications.  The  following  directions  should  be  observed 
in  connection  with,  the  present  system:  (a)  One  stick  relay 
should  be  provided  for  each  route,  (b)  Of  the  two  stick  relays 
employed  for  the  electric  locking  of  one  piece  of  track  either 
one  must  always  be  energized,  (c)  The  stick  relay  pick-up  wire 
and  stick-up  wire  must  be  selected  to  take  care  of  various  line- 
ups and  all  stick  wire  selecting  contacts  should  be  arranged  to 
make  before  break,  (d)  The  lock  wire  should  be  selected  the 
same  as  the  pick-up  and  stick-up  wires,  (e)  Both  ends  of  the 
lock  wire  should  go  to  battery  through  a  stick  relay  point,  (f) 
One  lever  lock  is  necessary  for  each  end  of  a  crossover. 

Comments.  This  scheme  will  work  equally  well  with  lock 
relays  as  well  as  lever  locks.  The  advantage  lies  in  the  elimina- 
tion of  the  back  point  lock  control  and  the  few  complications  en- 
countered when  applying  the  circuit  at  large  plants.  The  dis- 
advantage lies  in  the  additional  number  of  lever  locks  and  select- 
ing contacts  and  the  increased  amount  of  wire  required.  When 
making  comment  upon  complications  in  a  circuit  this  does  not 
refer  to  the  work  involved  in  the  design  of  the  circuit,  but  ap- 
plies to  the  circuit  installed  and  the  trouble  and  tribulations  of 
a  maintainer  when  hunting  causes  for  failures  and  the  delays 
such  failures  will  cause  to  traffic  at  the  plant. 

SCHEME  F. 

Description.  In  this  system  a  stick  relay  is  employed  for 
each  direction  of  traffic  and  for  every  track  section  beyond  the 
first  section  in  the  route.  Where  a  route  consists  of  more  than 
one  track  section,  however,  the  last  track  section  need  not  have 
a  stick  relay  connected  with  it.  It  is  only  necessary  that  the 
lever  locks  be  controlled  through  one  or  two  of  these  stick  relays 
in  addition  to  the  track  relay  for  the  section  in  which  the  switch 
is  located. 

171 


ELECTRIC    LOCK  IXC, 

Operation.  In  Fig.  179  it  will  be  noted  that  stick  relay 
marked  BE  (track  section  B  for  eastbound  electric  locking)  will 
drop  with  lever  8  reversed  when  the  train  enters  track  section  C. 
Hence  a  train  moving  with  signal  8  at  clear  will  de-energize  C 
locks  when  entering  track  section  C,  and  will  also  lock  B  and  A 

«  a  m' 


*~Ua 


"fitn 


FIG.   179. 


by  the  dropping  of  stick  relay  BE.  A  train  entering  B  section 
will  keep  B  and  A  locked,  and  a  train  entering  section  A  will 
release  stick  relay  BE,  which  will  pick  up.  With  a  movement  in 
the  opposite  direction  signal  1  will  be  cleared  and  the  train 
entering  section  A  will  drop  stick  relay  BW  while  BE  will  stay 
up.     The  operation  will  be  identical  with  the  train   movement 

,    d  c  a      •         a  -CU 

~Oa 


H 


\/  Bt 


FIG.    180. 


FIG.   181. 


described  with  signal  8  cleared.  In  Fig.  180  westbound  train 
movements  will  be  protected  by  BW  and  CW  stick  relays  and 
eastbound  movements  by  CE  and  BE  stick  relays.  The  latter 
relays  are  not  shown,  as  their  control  will  be  similar  to  that 
indicated.     Fig.  181  shows  the  selections  for  stick  relay  pick-up 

172 


SECTIONAL   ROUTE   LOCKING 

and  stick-up  wires.  The  sectional  route  locking  is  assumed  to  be 
effective  with  signal  1  cleared,  while  for  electric  locking  in  the 
opposite  direction  the  arrangement  will  have  to  be  duplicated. 
Westbound  stick  relays  are  required  for  track  sections  B  and  C, 
as  shown,  and  the  same  for  eastbound  train  movements.  Selec- 
tion whereby  BW  is  shunted  out  of  track  section  A  and  signal  1 
when  switch  2  is  reversed  is  necessary.  CW  relay  can  be  con- 
trolled through  BW;  stick  relay  instead  of  the  track  sections  and 
can  shunt  out  when  3  is  reversed.  With  lever  4  reversed  CW 
will  be  controlled  by  other  signals  and  track  sections,  as  explained 
in  previous  systems. 

Applications.  In  regard  to  how  to  apply  the  present  system 
the  following  will  be  of  value:  (a)  Every  section  in  a  route 
except  the  first  and  the  last  section  will  have  two  stick  relays. 
The  stick  wire  for  each  is  to  be  controlled  through  a  signal 
lever  and  selected  through  switch  levers,  and  the  pick-up  wire 
is  to  be  controlled  through  all  sections  in  advance,  (b)  The 
stick  relay  must  not  drop  when  manipulating  any  lever  on  which 
it  is  selected,  (c)  Where  a  route  consists  of  two  track  sections 
only  the  last  section  will  have  a  stick  relay,  (d)  Where  a  stick 
relay  is  employed  for  one  section  in  advance  of  another  the  next 
stick  relay  can  be  controlled  through  a  front  point  of  this  relay 
instead  of  through  the  track  relays.  The  locks  will  take  battery 
from  one  direction  only  through  one  or  two  stick  relays  and  a 
track  relay,  (e)  Only  one  lever  lock  is  necessary  for  a  cross-over, 
(f)  Lever  locks  need  not  be  selected. 

Comments.  For  simplicity  in  design  and  on  account  of  the 
limited  number  of  selecting  and  track  relay  contacts  required, 
the  present  system  cannot  be  excelled,  although  the  additional 
number  of  stick  relays  required  when  a  route  consists  of  a  con- 
siderable number  of  track  sections  might  be  considered  a  dis- 
advantage by  some  engineers. 

SCHEME  G. 

Description.  Like  the  scheme  just  described,  scheme  G  em- 
ploys one  stick  relay  for  each  direction,  and  for  each  section 
following  the  first  track  section.  In  the  present  system,  how- 
ever, the  stick  relays  drop  when  the  signal  is  cleared  and  do  not 

173 


ELECTRIC    LOCK  IXC 

pick  up  until  the  train  has  entered  the  track  section  in  which 
the  lock  to  be  released  is  located.  This  scheme  is  arranged 
on  the  order  of  a  stick  locking'  circuit  in  that  the  locking  takes 
effect  upon  the  clearing  of  a  signal  whether  a  train  enters  the 
route  or  not. 


c 


y* 


M 


B+ 


ni 


FIG.    182. 


S^BK 


\/  B+ 


B 


@_ 


FIG.   183. 


£U 


\/  /9/ 


Operation.  In  Fig.  182  the  scheme  is  shown  applied  to  trains 
running  in  the  direction  of  the  arrow.  It  will  be  noted  that 
the  clearing  of  signal  1  will  drop  stick  relay  BW,  which  again 
will  drop  CW  relay.  A  train  entering  section  B  will  pick  up  BW 
stick  relay  and  upon  entering  section  C,  CW  relay.  For  train 
movements  in  the  opposite  direction  a  stick  relay  for  sections  B 
and  A,  designated  BE  and  AE,  will  be  necessary.  By  con- 
trolling locks  A  through  stick  relays  BW,  AE  and  track  relay 
A ;  locks  B  through  BW,  BE  and  track  relay  B  ;  and  locks  C 
through  CW,  BE  and  track  relay  C,  sectional  route  locking  and 
stick  locking  will  be  provided  for  train  movements  in  both  direc- 
tions.    The  stick  relay  circuit  can  be  arranged  as  shown  in  Fig. 


D 


6 


a  ni 


c 


mm 


C 


LB+ 


r—L  s+        r—~8± 


Bi- 


^LM 


6y  B+ 


FIG.   184. 


183.  Here  only  one  stick  relay  (BW)  is  necessary  for  one  direc- 
tion, this  stick  relay  picking  up  in  track  section  C.  With  this 
arrangement,  locks  in  section  A  cannot  be  controlled  through 
the  stick  relay,  as  they  would  not  be  released  until  section  C 
was  reached  by  the  train.     Thus  the  dropping  of  B  W  relay  when 

174 


SECTIONAL    ROUTE    LOCKING 

clearing  signal  1  would  not  drop  locks  in  section  A,  but  these 
locks  would  be  de-energized  by  the  train  entering  section  A.  The 
locks  in  C  would  be  controlled  through  relays  BW  and  BE  in 
series.  With  the  circuit  as  arranged  in  Fig.  18,  but  with  a 
different  layout,  the  circuit  for  a  train  movement  in  one  direc- 
tion will  be  arranged  as  in  Fig.  184.  No  description  should  be 
necessary  except  that  the  reverse  lever  contact  6,  which  is  used 
in  multiple  with  pick-up  circuit  for  stick  relay  DW,  is  employed 
so  that  stick  relay  DW  will  pick  up  even  if  a  train,  moving  under 
a  clear  westbound  signal,  should  stop  ahead  of  signal  6  with- 
out entering  track  section  D.  Hence  the  clearing  of  signal  1 
will  drop  stick  relay  DW,  and,  if  the  train  stops  ahead  of  signal 
6  for  a  back-up  movement,  the  clearing  of  this  signal  will  again 
pick  up  stick  relay  DW.  The  application  should  readily  be 
understood  from  the  description  made. 

Comments.  The  advantages  of  system  G  are:  (1)  the  require- 
ments of  few  selections  and  track  relay  points,  and  (2)  the 
simple  manner  in  which  the  circuits  can  be  arranged.  The  disad- 
vantage is  the  apparent  inconsistency  when  considering  that 
section  route  locking  is  applied  to  an  interlocking  to  improve 
flexibility  and  facility  in  train  operations.  Should  the  leverman 
in  the  present  system  clear  a  wrong  signal  the  route  would  be 
tied  up  until  the  manipulation  of  a  time  release  would  again  re- 
store the  plant  to  normal  operating  conditions.  There  are  many 
engineers,  however,  who  rightly  insist  upon  procuring  the  pro- 
tection given  by  stick  locking  in  all  applications  of  electric  lock- 
ing at  interlockings  under  their  jurisdiction  and  who  keep  the 
leverman  responsible  for  any  delay  to  train  movements  caused 
by  errors  on  his  part. 

SCHEME  H. 

Description.  Scheme  H,  which  is  another  stick  locking  ar- 
rangement method  of  securing  sectional  route  locking,  employs 
two  stick  relays  for  each  route.  Both  relays  will  drop  with 
the  clearing  of  a  signal,  one  stick  relay  picking  up  on  the  first 
track  section  in  the  route,  and  the  other  on  the  last  section.  The 
arrangement  will  have  to  be  duplicated  for  protection  to  train 
movements  in  the  opposite  direction. 

175 


ELECTRIC   LOCKING 

Operation.  Fig.  185  shows  a  circuit  applied  to  a  train  move- 
ment in  the  direction  of  the  arrow.  The  present  circuit  can  only 
be  applied  to  interlocking  plants  where  lock  relays  are  employed 
as  a  locking  medium.  With  the  clearing  of  signal  1  both  stick 
relays  IS  and  1SX  will  drop  in  turn  all  lock  relays  for  sections 


1B+ 


FIG.   185. 

A,  B,  C  and  D.  A  train  entering  section  A  will  pick  up  stick 
relay  IS,  while  stick  relay  1SX  will  remain  de-energized.  When 
a  train  clears  track  section  A  current  will  be  applied  to  lock  relay 
A  through  stick  relay  IS,  the  same  process  re-occurring  for  each 
of  the  sections  in  sequence.  Stick  relay  1SX  will  pick  up  in 
section  D.  It  will  be  noted  that  each  lock  relay  is  controlled 
through  a  point  on  another.  For  this  reason  a  train  moving  in  a 
direction  opposite  to  the  arrow  would  keep  the  lock  relays  behind 
it  de-energized  as  it  moved  along.  By  the  employment  of  stick 
relay   1SX   this   is  prevented,  because   when   a  train   enters   the 


His 


MfTffinffirffi 


FIG.   186. 


FIG.   187. 


route  with  signal  8  at  clear,  stick  relay  1SX  will  stay  picked  up 
and  each  lock  relay  will  be  connected  to  battery  through  a  front 
point  of  this  relay  is  multiple  with  the  lock  relay  ahead  of  it. 
For  sectional  route'  locking,  with  signal  8  at  clear,  two  more 
stick    relays    would    be    required,   both    controlled    in    the    same 

176 


SECTIONAL    ROUTE    LOCKING 

manner  as  the  stick  relays  in  the  figure,  except,  of  course,  that 
lever  8  would  drop  both  relays,  and  one  would  pick  up  in  section 
D  and  the  other  in  section  A.  The  lock  relays  should  take  com- 
mon through  the  stick  relays  and  other  lock  relays  in  multiple, 
as  shown  in  Fig.  186. 

Comment.  The  same  comments  as  made  with  the  previous 
scheme  will  also  apply  to  the  one  under  discussion.  It  is  evident 
that  this  scheme,  with  a  few  modifications,  can  also  be  applied 
to  a  plant  in  which  lever  locks  are  employed. 

SCHEME  J. 

Description.  A  stick  relay  for  every  track  section  is  necessary 
in  scheme  J.  Each  stick  relay  will  pick  up  as  the  train  enters 
the  section  to  which  it  is  applied,  and  the  locks  by  receiving 
battery  through  a  front  point  of  the  track  relay  and  the  stick 
relay  will  be  released  as  the  train  passes  out  of  each  track  section. 

Operation.  Fig-.  187  shows  a  simple  application  of  this 
system  for  a  train  movement  in  the  direction  of  the  arrow.  A 
train  entering  section  A  will  pick  up  stick  relay  AS  for  this 
section.  The  train  clearing  section  A  and  having  entered  section 
B  will  pick  up  stick  relay  BS,  which  in  turn  will  stick  up  relay 
AS  through  front  point  of  BS  and  AS.  Lock  A  will  be  released 
through  front  point  of  track  relay  A  and  stick  relay  AS.  With 
the  train  in  section  C,  all  the  stick  relays  will  be  energized.  A 
train  having  cleared  the  route  will  again  drop  the  stick  relays. 
With  certain  modifications  the  system  can  be  made  applicable 
for  sectional  route  locking  in  both  directions. 

Com  mf. nts.  The  advantage  in  this  system  is  that  section 
31  route  locking  will  take  effect  when  a  train  enters  a  route  with 
a  signal  at  clear  or  danger.  The  disadvantages  are  the  number 
of  stick  relays  required,  and  the  complications  which  a  complex 
signaled  layout  will  offer  in  the  design  and  maintenance  of  the 
system. 

FLEXIBILITY  OF  MECHANICAL   LOCKING 

Closely  associated  with  sectional  route  locking  the  mechanical 

dog  locking  in  the  interlocking  machine  must  be  sufficiently 

177 


ELECTRIC   LOCKING    ■ 

flexible  so  as  to  allow  the  releasing  to  be  effective  while  also 
rigid  enough  to  give  protection  to  the  trains.  Thus  in  many  in- 
stallations where  sectional  route  locking"  is  applied  signal  locking 
only  is  employed,  that  is,  signal  levers  lock  all  switches  and  derails 
in  their  route;  the  switch  levers  do  not  lock  any  levers,  and  the 
derail  levers  only  lock  derails  in  conflicting  routes.  In  other 
installations  the  derails  lock  all  facing  point  switches  in  the  route, 
thereby  allowing  the  line-up  of  any  diverging  route  after  the 
train  has  passed  the  derail  and  the  facing  point  switch.  At  other 
places  the  high  speed  facing  point  derails  will  lock  all  switches 
and  derails  in  the  route,  thereby  providing  flexibility  in  follow- 
ing high  speed  movements,  but  not  in  slow  speed  movements.  In 
other  places  the  derails  are  used  for  locking  of  routes  while 
at  the  same  time  the  system  of  locking  is  devised  so  that  the 
flexibility  in  lever  operation  allowed  by  the  electric  locking  is 
retained.  This  can  be  done  by  having  the  facing  derail  lock 
all  the  trailing  derails  and  facing  point  switches  in  their  route. 
In  most  installations  where  special  release  is  required  the  me- 
chanical locking  is  transferred  from  the  derails  to  the  signals  to 
allow  necessary  freedom.  The  protection  which  may  be  lacking 
by  the  absence  of  switch  locking  is  generally  provided  by  having 
the  signals  controlled  through  all  conflicting  derails  with  certain 
line-up  of  switches  to  insure  the  proper  operation  and  correct 
position  of  such  derails.  At  mechanical  plants  it  is  important 
that  the  levers  for  the  operation  of  the  facing  point  locks  are 
arranged  with  due  consideration  to  the  facilities  of  release  which 
the  electric  locking  will  provide. 

ADJUNCTS. 

Lever  Lights.  Sectional  route  locking  being  applied  at  inter- 
locking plants  having  congested  traffic,  it  is  of  advantage  to  indi- 
cate the  occupancy  of  a  track  section  or  the  electric  unlocking  of 
a  switch  to  the  leverman.  This  can  be  accomplished  by  placing 
a  small  light  on  the  top  of  each  switch  lever  and  having  it  con- 
trolled in  multiple  with  the  lever  lock,  showing  at  all  times 
whether  the  lock  can  be  energized  or  not.  When  the  light  is 
burning  the  track  is  free,  but  when  the  light  is  out  the  track  is 
occupied  and  the  lexer  must  not  be  moved.  If  it  is  desired  to 
use  lights  on  the  signal  levers  to  show  when  the  routes  controlled 
by  those  signals  are  unoccupied,  a  light  may  be  placed  in  series 

178 


SECTIONAL    ROUTE    LOCKING 

or  in  multiple  with  the  stick  relay  controlled  by  the  signal  and 
used  in  the  sectional  route  locking",  or  a  relay  may  be  so  placed 
to  control  the  light. 

Emergency  Release.  In  sectional  route  locking  emergency 
releases  or  time  releases,  as  employed  in  connection  with  section 
and  route  locking,  cannot  be  employed  as  it  would  tend  to  intro- 
duce additional  complications  in  an  ordinarily  complicated  cir- 
cuit. Hence  if  it  becomes  necessary  to  change  a  switch  or  a 
derail  ahead  of  a  train  which  has  come  to  a  stop,  current  is  gen- 
erally supplied  to  the  lever  locks  by  means  of  a  push  button  or 
a  snap  switch.  This  switch  is  often  located  at  a  distance  from 
the  interlocking  machine  so  that  it  takes  two  men  to  release  a 
route,  one  to  push  the  button  or  switch  and  another  to  throw 
the  lever  while  the  button  is  being  held.  The  switch  or  button 
is  of  a  style  which  will  replace  itself  to  the  normal  position  if 
left  after  the  release  is  accomplished  and  the  releas  circuit  will 
not  shunt  out  the  track  relay  in  which  the  train  is  standing. 

Conclusion.  When  deciding  upon  what  system  of  sectional 
route  locking  to  employ  a  number  of  points  must  be  considered, 
viz.,  cost  of  installation,  complications  in  design,  complications 
and  possible  traffic  delay  in  maintenance,  protection  for  following 
train  movements  and  numerous  others.  In  this  limited  space 
it  is  not  possible  to  cover  each  system  in  detail  as  much  as  could 
be  desired.  It  is  believed,  however,  that  this  chapter  will  give 
the  proper  conception  as  to  the  virtues  and  drawbacks  of  a  num- 
ber of  schemes  from  which  poor  features  can  be  eliminated  and 

good  features  added  to  make  them  suitable  for  the  needs  and 
requirements  of  various  plants.  In  all  schemes  described  it  is 
of  course  possible  to  provide  combined  protection  by  adding 
features  necessary  for  such  protection.  For  example,  stick  or 
approach  locking  may  be  added  to  the  sectional  route  locking 
by  having  the  stick  relay  for  the  former  control  the  stick  relay 
for  the  latter.  In  a  similar  manner  other  classes  of  electric  lock- 
ing may  readily  be  combined  with  sectional  route  locking. 


179 


X 

CHECK   LOCKING 

Definition.  Check  locking,  according  to  the  Railway  Signal 
Association's  definition,  is:  "A  method  of  interlocking,  electri- 
cally, the  levers  in  two  adjacent  interlocking  plants  to  permit 
train  movements  between  them  to  be  made  safely  against  the 
current  of  traffic  and  as  the  result  of  co-operation  at  the  inter- 
lucking  stations  concerned."  It  will  be  recalled  that  one  require- 
ment at  an  interlocking  plant,  when  arranging  the  dog  locking 
in  the  machine,  is  to  so  interlock  the  two  signal  levers  govern- 
ing the  movement  of  trains  on  a  given  piece  of  track  as  to  pre- 
vent the  simultaneous  entrance  of  trains  from  opposite  direc- 
tions. In  one  machine  this  can  readily  be  done  mechanically,  but 
where  the  levers  to  be  interlocked  are  located  in  two  separate 
interlocking  machines  placed  in  a  tower  a  short  distance  apart, 
this  cannot  be  accomplished  mechanically  but  electrical  means 
must  be  resorted  to.  Briefly,  check  locking  shall  prevent  the 
simultaneous  entrance  of  trains  from  opposite  directions  onto 
a  piece  of  given  track  and  insure  that  the  operators  in  both 
towers  are  "working  together,"  or  insure  the  co-operation  of 
levermen   in   two  adjacent  towers. 

Where  Emi-loved.  Check  locking  i>  employed  at  interlock- 
ings  situated  close  together,  >  ( a )  where  the  arrangement  of 
switches  and  signals  is  such  that  it  would  be  of  advantage  to 
make  use  of  the  same  track  under  special  conditions  or  (b)  where 
local  conditions  such  as  tunnels,  trestles  or  bridges  prevent  the 
construction  of  more  than  one  track  (or  "gauntlet  track")  be- 
tween two  adjacent  interlocking  plants.  Thus  in  the  one  case 
check  locking  can  be  employed  to  advantage  to  facilitate  the 
operation  of  a  large  number  of  trains  and  add  to  the  flexibility 
of  two  or  more  tracks  between  interlockings  ;  in  other  words,  it 
will  readily  accomplish  the  change  of  normal  current  of  traffic 
with  maximum  safety  at  a  minimum  expense.  In  the  second 
case  it  comes  near  being  a  substitute  for  single  track  controlled 
manual  blocking  and,  in  fact,  this  may  be  said  to  be  true  of  any 
effective    form   of   check   locking. 

Requirements.  1.  Check  locking  should  be  made  effective 
with  the  clearing  of  a  signal,  permitting  the  entrance  of  a  train 

180 


CHECK   LOCKING 

onto  a  piece  of  given  track  which  leads  to  an  adjacent  interlock- 
ing plant. 

2.  The  check  locking  effect  should  be  made  permanent  while 
the  train  is  moving  between  the  signals  governing  the  opposing 
movements  over  the  common  piece  of  track. 

3.  Check  locking  can  be  made  effective  for  train  movements 
in  one  direction  or  in  both  directions. 

There  are,  broadly  speaking,  two  classes  of  check  locking, 
viz. :  (a)  where  it  is  applied  to  give  preference  as  to  direction  of 
traffic  and  (b)  where  no  preference  is  given  as  to  direction  of 
traffic. 

With  the'Use  of  Check  Lock  Levers.  In  order  that  the 
simplest  circuits  with  a  limited  number  of  instruments  be  ob- 
tained the  best  arrangement  possible  at  large  interlocking  is  with 
the  use  of  an  independent  lever  in  each  machine.  The  levers  em- 
ployed are  generally  termed  check  lock  levers  (also  traffic  levers 
and  master  levers)  and  to  these  levers  the  electric  locking  pro- 
vided is  applied.  As  a  rule  each  track  over  which  reverse  train 
movements  between  the  interlockings  are  to  be  permitted  is  pro- 
vided with  a  check  lock  lever. 

Arrangement  of  the  Mechanical  Locking.  At  interlock- 
ing plants  where  it  is  desirable  to  employ  a  separate  lever  in  the 
interlocking  machine,  as  a  check  lock  lever,  and  where  there  is 
preference  as  to  the  direction  of  traffic,  the  mechanical  locking 
in  the  interlocking  machine  should  be  arranged  so  that  when  the 
check  lock  levers  are  in  their  normal   position   the   signal  lever 

/Locks  ^  n  .  „  /Stocks  (&>    n-</5 


"7TJ  — [J 

Check  lock  lever  pj  Check  lock  lever  *I6  ^ 

A  B 

B-h  1,  £j  J6   8/ 


FIG.   188. 


for  the  reverse  movement  should  be  locked  normal  and  the  sig- 
nal lever  for  movements  with  the  current  of  traffic  should  be 
free  to   move.     When   the   check  lock   levers   are   reversed   the 

181 


ELECTRIC   LOCKING 

signal  lever  for  movements  with  the  current  of  traffic  should 
be  locked  normal  while  the  reverse  movement  signal  (generally 
a  dwarf  signal)  should  be  unlocked  and  in  position  to  be  cleared. 
The  locking  arranged  in  accordance  with  the  above  is  shown  in 
Fig.  188.  This  is  a  simplified  layout  showing  a  single  track 
where  the  normal  current  of  traffic  is  from  tower  A  towards 
tower  B.  Here  in  tower  A  check  lock  lever  1  locks  signal  lever 
2  normal  and  in  tower  B  signal  lever  15  locks  check  lock  lever 
16  reversed. 

Where  there  is  no  preference  as  to  the  direction  of  traffic  the 
check  lock  levers  when  in  the  normal  position  will  lock  the  sig- 
nals governing  the  opposing  movements  normal,  while  the  check 
lock  levers  when  in  the  reverse  position  will  unlock  the  signal 


TH 


Check  lock  /ei/er  al6 


A  B 

Z 


-Srt; — ^  ^ — a-tr^ 

in  mi 

FIG.   189. 

levers.  This  is  illustrated  in  Fig.  189  where  signal  lever  2  locks 
check  lock  lever  1  (tower  A)  reversed,  and  a  similar  arrange- 
ment is  made  at  tower  B. 

Traffic  Direction  Preference.  Check  locking,  giving  pref- 
erence as  to  direction  of  traffic,  is  generally  used  in  connection 
with  two  or  more  track  systems.  Fig.  188  shows  a  circuit  giving 
traffic  direction  preference  and  as  the  normal  direction  is  from 
tower  A  to  B,  as  shown  by  the  arrow,  signal  2  is  free  to  be 
cleared  at  any  time  without  interference  from  the  check  lock- 
ing. In  order  to  clear  signal  15,  permitting  a  movement  against 
current  of  traffic,  the  check  lock  levers  in  both  towers  must  be  re- 
versed ;  lever  1  in  order  that  lock  on  lever  16  can  be  energized 
and  lever  16  in  order  that  15  can  be  released.  With  lever  1  re- 
versed signal  lever  2  is  locked  normal.  The  lock  on  lever  1 
will  necessarily  be  a  reverse  lock  which  will  hold  this  lever 
locked  until  16  is  placed  normal  again.  Lever  lock  on  16  is  a 
normal  lock  which  prevents  the  release  of  the  lever  until  1   is 

182 


CHECK    LOCKING 

reversed.  Relay  Z  represents  the  contacts  or  combinations  of 
selections  taking  place  between  the  towers  to  prevent  the  release 
of  the  check  locking"  until  the  route  is  completely  traversed  by  the 
train.  With  the  arrangement  as  shown  it  is  evident  that  it  is 
impossible  to  have  a  condition  existing  which  would  permit  the 
two  opposing  signals  2  and  15  to  be  cleared  simultaneously. 

Another  method  with  a  traffic  direction  preference  arrange- 
ment is  the  use  of  only  one  check  lock  lever  in  the  direction  of 
traffic  and  the  opposing  signal  inter-connected  electrically  with 
the  check  lock  lever.     In  Fig.  190  the  stick  relay  C  at  tower  B 


n 

H 

nr 

Cm  6 
Lev 

-1 

CK  Lock      ,-. 

« ife  n    | 

^_^_^ 

-a 

0 

A 

t              e+ 

"Us 

n, 

Control, 

TJ 

Sl&.  T 

B 

Ofo     B+- 

I 

1    Ifel 

* ■ — c 

t 

Control 

Sifc.S 

Id 

py*1 

FIG.  190. 

will  make  cooperation  between  the  towers  compulsory,  as  the 
pressing  of  the  hand  key  D  and  energization  of  relay  C  will  ad- 
mit the  complete  reversal  of  check  lock  lever  16  in  tower  B. 
The  operation  of  signals  T  and  S  can  only  be  accomplished  with 
the  completion  of  the  movement  of  lever  16  in  either  direction, 
as  shown. 

Xo  Traffic  Direction  Preference.  Fig.  189  shows  a  cir- 
cuit where  there  is  no  preference  as  to  direction  of  traffic  and 
this  scheme  is  employed  at  single  track  roads  or  tracks  being  of 
gauntlet  construction  or  in  a  tunnel.  Here,  in  order  to  clear  signal 
2,  check  lock  lever  1  must  be  reversed  and  in  order  to  reverse  lever 
1  check  lock  lever  16  (tower  B)  must  be  normal.  By  reversing 
lever  1,  lever  16  is  locked  normal  and  consequently  levers  1  and 
16,  and  again  levers  2  and  15  cannot  be  reversed  at  the  same 
time.  Locks  on  levers  1  and  16  are  full  normal  locks  and  Z  re- 
lay represents  the  track  sections  between  signals  2  and  15. 

Tower  Director  Control.  At  places  where  directors  are  em- 
ployed to  supervise  the  handling  of  trains  it  is  important  that 

183 


ELECTRIC    LOCK  IXC, 


the  circuit  be  arranged  so  that  the  check  lock  levers  will  not  be 
released  without  their  consent.  A  circuit  including  such  a  pro- 
vision is  shown  in  Fig.  191.  This  is  a  no-traffic  preference 
scheme  and  the  hand  keys  marked  Y  are  the  tower  director's 


--f(7) 


<5bck?  %  n  /5, 


Check  lock  lever    / 

A 

Bf  y      i  y 

-is— 


Check  Ijck  le*ei    ,  .' 


°£ 


B 


M 


FIG.   191. 


release  keys.  In  order  that  check  lock  lever  1  (tower  A)  can 
be  released  the  director  must  press  the  key  Y  and  this  will  also 
remove  positive  battery  from  lever  16  at  tower  B.  Additional 
lever  contacts   can  be  employed   in   this   circuit  as   amplified   in 


Fig.  189. 


Without  the  Use  of  Check  Lock  Levers.  The  protection 
of  a  layout  as  in  Fig.  189  can  readily  be  accomplished  without 
the  employment  of  check  lock  levers.     Fig.   192  shows  such  an 

n  i€ 


-  5    C 


TJ/ 


U£ 


A 


FIG.   192. 


ill.     hl_ 


B+  J 


A 


°r 


FIG.    193. 


/S 


*"--.    16  Locks  CL 


B 


HZL 


arrangement  where  advance  signal  levers  2  and  15  reversed  are 
locked  by  the  home  signal  levers,  the  advance  signal  levers  thereby 
acting  as  check  lock  levers.  A  normal  lock  is  to  be  placed  on 
the  advance  signal  levers  and  the  locks  controlled  as  in  Fig.  189. 

184 


CHECK    LOCKING 

"Advance  Signal"  Arrangement.  In  Fig.  193  an  arrange- 
ment is  shown  where  the  advance  signal  tor  interlocking  B  is 
used  as  a  distant  signal  for  interlocking  and  check  locking  is 
provided  by  the  employment  of  a  normal  lock  on  home  signal 
lever  15.  The  procedure,  when  permitting  a  train  movement 
from  11  to  A,  will  he  that  signals  2  and  1  are  cleared  from  tower 
A.  Signal  1  cleared  will  close  contact  X  on  signal  circuit 
breaker  and  break  contact  Y.  This  will  drop  indicator  I  in 
tower  B,  thereby  indicating  to  the  operator  that  lever  15  is 
released.  Lever  lock  15  will  take  battery  through  contact  X 
at  signal  1.  through  all  intervening  track  relays  Z,  contact  on 
its  own  lever  and  back  point  of  indicator  I.  The  arrangement 
will  have  to  be  duplicated  for  a  train  movement  from  tower 
A  to  B,  when  signal  S  will  be  the  advance  signal  and  the  other 
appliances  be  located  in  tower  A. 


Tower  Lock  Instrument.  Check  locking  can  also  be  pro- 
vided through  the  medium  of  tower  lock  instruments  or  so-called 
electrically  locked  circuit  controllers.  These  circuit  controllers 
are  employed  to  pick  up  relays  which  again  act  as  control  or 
slotting  relays  for  the  signals  permitting  the  opposing  train 
movements  to  take  place.     In  Fig.  194,  I  and  H  are  tower  instru- 


TJ/ 


Q 


*$-*-> 


~M7^  Co"!  ■;' 


SlQnGl     1 


FIG.    I'M. 


Control 
signal*IS 


ments  normally  energized,  and  F  and  G  relays  used  for  the  control 
of  signals  1  and  15  respectively.  In  order  to  permit  a  train  move- 
ment from  tower  15  to  A  levers  1  and  15  must  be  normal.  The 
clearing  of  signal  16,  and  with  instruments  I  and  II  in  the  normal 
position,  relay  G  will  pick  up.  The  reversal  of  lever  15  will 
clear  this  signal  through  a  contact  on  relay  G.  As  wire  X  is 
used  solely  for  the  purpose  of  energizing  the  control  relays   F 

185 


ELECTRIC   LOCKING 

and  G,  this  wire  can  be  selected  through  switches,  derails  and 
track  relays  so  that  the  signal  control  wire  proper  needs  only  to 
be  broken  through  either  relay.  For  a  train  movement  from  A 
to  B,  both  tower  instruments  must  be  reversed  and  signal  2  re- 
versed, when  relay  F  will  pick  up  through  reverse  contact  L 
on  instrument  H  and  reverse  contact  K  on  I  and  wire  X.  The 
traffic  preference  is  obviously  from  tower  B  to  A. 

At  Power  Interlockings.  At  power  interlockings  where 
check  lock  levers  are  employed  the  arrangement  generally  used  is 
to  control  the  indication  magnet  in  the  interlocking  machine  in 
the  manner  shown  in  Figs.  188  and  189.  The  special  indication 
schemes  employed  at  such  plants  are  generally  of  necessity  modi- 
fied so  as  to  actuate  the  indication  magnet  by  a  battery  indication 
arrangement.  The  other  schemes  are  also  applicable  to  power 
interlockings. 

Additional  Protection.  As  an  extra  precaution  the  lock  on 
the  check  lock  lever  may  be  controlled  in  series  through  contacts 
on  all  signal  arms  controlled  by  the  interlockings,  in  addition 
to  a  contact  on  the  signal  lever,  thereby  insuring  that  all  signals 
have  assumed  the  stop  position  before  the  lever  is  released.  As 
in  other  styles  of  electric  locking  the  lever  lock  when  placed  on 
a  signal  lever  may  be  modified  and  the  circuit  arranged  so  that 
section  locking  and  indication  locking  will  be  provided  in  addition 
to  the  check  locking. 


186 


XI 

OUTLYING  SWITCH  LOCKING 

General.  Protection  provided  by  the  electrical  locking  of  out- 
lying switches  can  be  defined  as  being  electric  locks  controlled 
from  a  signal  tower  and  attached  to  the  operating  connections 
of  outlying  switches  to  prevent  a  switch  from  being  moved  with- 
out the  knowledge  and  consent  of  the  tower  operator  or  lever- 
man.  At  mechanical  interlockings  it  frequently  happens  that  a 
switch  or  a  crossover  is  located  between  the  home  and  distant 
signal  or  between  the  dwarf  and  the  advance  signal,  consequently 
close  to  the  tower,  but  still  too  far  to  be  safely  operated  from 
there  with  mechanical  connections.  At  power  interlockings, 
where  the  same  conditions  may  exist,  it  might  be  found  unde- 
sirable to  take  such  outlying  switches  into  the  interlocking,  due 
to  the  additional  signals  required.  In  all  such  cases  the  common 
practice  is  to  lock  the  switches  from  the  interlocking  tower  and 
have  the  trainmen  operate  the  switch  by  means  of  a  regular  switch 
stand.  The  arrangement  is  to  place  the  control  in  the  hands  of 
the  leverman  in  the  interlocking  tower.  He  may  thus,  under 
certain  restrictions,  unlock  the  switch  for  the  benefit  of  any 
train,  provided  conditions  are  right  for  its  use. 

Mechanical  Arrangement.  The  earliest  practice  of  such 
control  of  outlying  switches  at  mechanical  interlockings  was  to 
apply  a  mechanically  connected  bolt  lock  to  the  switch  or  lock 
it  by  means  of  a  plunger  lock,  either  one  of  which  was  operated 
from  an  interlocked  lever.  Such  arrangements  are  also  installed 
in  the  present  day  practice  where  the  expense  of  more  reliable 
protection  is  not  warranted.  When  bolt  locks  are  used  the  switches 
are  generally  equipped  with  front  rods,  lock  rods  and  a  usual 
bolt  lock  casting.  The  bolt  lock  rod  is  fastened  to  the  switch 
point  or  the  front  rod  and  by  means  of  notches  in  the  two 
bars  the  switch  can  be  locked  and  unlocked.  The  rods  have  only 
one  notch  each,  so  that  the  switch  can  only  be  locked  in  its 
normal  position.  In  this  way,  when  the  switch  is  to  be  operated 
the  leverman  unlocks  it,  and  he  cannot  again  lock  it  until  the 
switch  has  been  placed  in  the  normal  position  again.  With  a 
plunger  lock  the  method  of  operation  is  the  same.  The  switch 
is  equipped  with  a  Jock  rod  and  plunger  stand,  the  lock  rod  being 

187 


ELECTRIC    LOCK  IXC 

drilled  with  only  one  hole,  as  previously  discussed,  whereby  the 
switch  is  unlocked  and  locked  only  in  one  position.  The  ar- 
rangement of  locking  an  outlying  switch,  with  the  use  of  a  key, 
which  is  kept  by  the  man  in  the  nearest  tower,  has  also  been 
used  to  a  limited  extent.  This  method,  however,  is  far  from  satis- 
factory, and  causes  too  many  delays  to  be  practical  on  busy  lines. 

Electrical  Arrangement.  The  electrical  locking  of  an  out- 
lying switch  can  be  accomplished  in  numerous  ways.  For  in- 
stance, at  the  switch  a  one-lever  dwarf  machine  may  be  provided, 
whose  lever  locks  the  switch  in  the  desired  position,  and  is  in 
turn  electrically  locked  from  the  tower  by  an  electric  lock.  An- 
other method  is  to  use  a  special  electric  switch  lock,  which  usually 
engages  with  the  switch  stand  and,  by  preventing  it  from  being 
operated,  keeps  the  switch  locked  in  the  desired  position.  In 
other  methods  the  electric  lock  will  engage  directly  with  the 
switch  rails  by  means  of  suitable  mechanical  connections.  This 
arrangement  is  possible  when  the  lock  is  a  combination  electric 
lock  and  switch  stand.  Protection  is  generally  provided  by  means 
of  the  lock  rod,  so  that  unless  the  lock  rod  assumes  its  proper 
position  when  the  switch  is  set  normal,  the  electric  lock  is  pre- 
vented from  assuming  its  normal  or  de-energized  position.  Elec- 
tric switch  locks  are  always  provided  with  electrical  contacts  for 
the  control  of  circuits  which,  in  most  cases,  are  employed  to  give 
an  indication  in  some  manner  to  the  leverman  that  the  switch 
has  been  placed  normal  and  locked  in  that  position.  In  the  tower 
the  electric  switch  lock  might  be  controlled  from  a  lever  in  the 
interlocking  machine,  which  is  interlocked  with  the  other  levers ; 
or  it  might  be  controlled  from  a  tower  instrument  or  hand  circuit 
controller,  which  is  usually  electrically  locked  by  the  switch  lock. 

Lever  Locking.  It  is,  of  course,  always  most  preferable  to 
have  the  switch  controlled  from  a  lever  in  the  interlocking  ma- 
chine so  that  the  proper  interlocking  between  it  and  the  signal 
lever  governing  movements  over  the  switch  can  be  provided. 
Such  levers  are  considered  as  F.  P.  L.  Levers,  and  the  swdtch 
lock  control  circuit  is  so  arranged  that  the  reversal  of  the  lever 
will  lock  the  switch  while  the  placing  of  the  lever  normal  will 
unlock  it.  The  signal  levers  governing  over  the  switch  will 
lock  the  switch  lock  lever  in  its  reverse  position.  Dwarfs  and 
slow-speed   signal   levers,   however,   should   not  lock   the  switch 

188 


OUTLYING    SWITCH    LOCKING 


lock  lever,  as  switch  movements  over  the  plant  should  he  per- 
mitted even  with  the  outlying  switch  lock  released. 

Hand    Switch    Control.     A    very    simple    outlying    switch 
lock  circuit  is  presented  in  Fig.  195.     A  hand  switch  "A"  when 

Of  T 


Hi    o 


o- 


FIG.    195. 


reversed  will  break  the  signal  control  circuit  and  release  the 
switch  lock  X.  The  switch  is  equipped  with  a  normal  lock  which 
prevents  the  release  of  the  lock  until  the  hand  switch  is  thrown. 
A  circuit  of  this  type  cannot  give  the  protection  required  by 
many  railroads,  viz.,  prevent  the  placing  of  the  signal  to  danger 
in  the  face  of  an  approaching  train  and  the  immediate  release 
of  the  switch  lock.  Furthermore,  no  provisions  can  be  made 
to  indicate  to  the  leverman  that  the  track  switch  has  been  placed 
normal  again  and  locked  in  that  position.  By  equipping  the 
switch  with  a  switch  box  and  control  signal  1  through  a  normal 
contact  on  same,  protection  to  insure  the  track  switch  being 
placed  normal  is  secured.  With  mechanically  operated  signals 
no  protection  against  the  simultaneous  clearing  of  signal  1  and 
release  of  the  switch  can  be  provided. 


TJZ     O 


1: 


r 


DrSTfeWT   Sl6 
CONTROL 


Re 


n* 


c 


CONTROL 


m 


Sl&NAL  1 


tr 


FIG.   196. 


Another  method  of  controlling  an  outlying  switch  lock  by 
means  of  a  hand  switch  or  hand  circuit  controller  is  shown  in 
Fig  196.  In  this  track  layout  an  advance  signal  is  included  to 
illustrate  the  combined  protection  usually  provided.     It  will  be 

189 


ELECTRIC    LOCKING 


noted  that  circuit  controller  A  when  in  the  normal  position  will 
control  the  distant  signal,  this  signal  in  the  present  case  being 
arranged  to  give  indication  for  signals  1  and  2.  The  reversal 
of  controller  A  will  break  the  distant  signal  control  circuit  and 
energize  switch  lock  X,  provided  signal  1  is  at  danger.  Signal  1 
can  only  be  cleared  when  the  switch  lock  armature  drops  into  the 
notch  in  the  segment  of  the  locking  dog,  and  this  can  happen 
only  when  the  track  switch  is  in  the  normal  position.  Circuit 
controller  A  can  also  be  used  as  an  emergency  switch  for  the 
release  of  any  type  of  route  locking  by  the  use  of  the  spare  con- 
tact. 


TJ. 


3±^     ^ 

IA     L_ 


~n 


FIG.    197. 


Indication  With  Hand  Switch  Control.  Fig.  197  shows  a 
more  elaborate  scheme,  which  provides  an  indication  to  show  that 
the  track  switch  is  locked  in  its  normal  position.  Signal  lever 
1  is  equipped  with  a  normal  lever  lock  of  the  type  carrying  con- 
tact springs  on  the  lock  armature,  so  that  the  switch  can  only 
be  released  when  the  lever  lock  is  resting  in  the  notched  seg- 
ment and,  consequently,  only  when  the  signal  lever  1  is  normal. 
The  outlying  switch  is  also  equipped  with  a  normal  lock  which 
carries  a  contact  spring  which  makes  only  when  the  lock  arma- 
ture drops  into  the  notched  segment  of  the  lock  dog.  This  con- 
tact, when  made,  will  energize  the  lock  on  lever  1.  While  the 
switch  is  reversed  the  lock  armature  rests  on  the  top  of  the  lock- 
ing dog  and  the  contact  is  thereby  broken.  This  insures  that  the 
switch  must  be  put  normal  before  the  contact  makes  for  the 
completion  of  the  signal  circuit. 

Hand  switch  or  key  A  has  two  positions,  one  of  which  will 
energize  the  switch  lock  provided  lever   1   is  normal,  and  the 

190 


OUTLYING    SWITCH    LOCKING 

hand   switch   in   the   other   position   will   energize   lever    lock    1 
provided  switch  lock  X  is  normal. 

Lever  Lock  Control.  As  previously  discussed,  when  a  lever 
in  an  interlocking  machine  is  employed  to  control  the  switch 
lock,  the  high  speed  signal  lever  should  lock  the  switch  lock 
lever  reversed  and,  as  the  switch  lock  lever  when  normal  un- 
locks the  switch,  the  switch  will  be  locked  as  long  as  the  signal 
is  at  clear.  There  should  also  be  some  type  of  route  locking  ap- 
plied to  the  high  speed  signal  lever  so  that  it  will  not  be  possible 
to  take  a  signal  away  from  an  approaching  train  and  immediately 
release  the  switch  lock  without  a  certain  time  interval.  It  is 
evident  that  one  lever  or  one  hand  switch  may  be  employed  to 
unlock  more  than  one  switch  and  for  this  reason  the  circuit  in 
Fig.    198  shows   a   circuit   arrangement   which   will   release   two 


— H    O 


FIG.   198. 

switch  locks  from  one  lever.  It  will  be  noted  that  the  normal 
position  of  lever  8  will  release  the  switch  locks  X  through  wire 
B,  both  switch  locks  being  connected  in  multiple.  The  lever 
lock  "A"  which  prevents  the  reversal  of  the  lever  unless  the 
switches  and  switch  locks  are  in  their  proper  position,  acts  as 
an  indication  to  this  effect  and  indirectly  prevents  the  clearing  of 
signal  1  until  the  route  is  completely  safe.  Lever  contact  D  acts 
as  a  cross-protection  contact  for  the  switch  locks.  The  front  con- 
tacts on  the  switch  locks  and  the  reverse  switch  box  contacts 
are  used  as  a  cross-protection  for  lever  lock  A  when  the  switch 
or  the  switch  lock  is  in  an  improper  position  for  the  energization 
of  the  lever  lock.  The  back  points  on  the  switch  locks  and  the 
normal  contacts  on  the  switch  box  are  used  for  the  energization 
of  the  lever  lock  A.    The  tap  on  indication  wire  E  can  be  em- 

191 


ELECTRIC    LOCKING 


ployed  for  the  control  of  signal  1  if  this  is  power  operated  or 
controlled.  In  this  way  the  signal  will  be  provided  with  the 
same  amount  of  cross-protection  as  that  given  the  lever  lock. 


L  Lock* 


8 
13 


FIG.   199. 

Fig.  199  shows  an  interlocked  lever  control  of  an  electric  lock 
placed  on  a  dwarf  lever  machine.  This  type  generally  has  a 
handle  which  can  be  turned  only  when  the  lock  is  unlocked  while 
the  handle  will  turn  a  commutator  for  the  make  and  break  of  cir- 
cuits. This  type  of  lock  also  usually  has  a  miniature  semaphore 
arm  which  acts  as  indication  of  the  position  of  the  lock  arma- 
ture to  the  trainman.  It  will  be  noted  that  the  control  of  the 
switch  lock  is  identical  with  the  previous  figure  and  that  the 
indication  and  cross-protection  is  provided  in  a  similar  man- 
ner, insuring  the  lever  lock  and  commutator  being  in  the  correct 
position  before  the  lever  lock   is   released. 

Tower  Instrument  Control.  Where  no  space  in  the  inter- 
locking machine  is  available  for  the  control  of  the  outlying 
switches  and  where  a  more  complete  protection  is  desirable  than 
that  procured  with  the  use  of  a  hand  switch,  tower  instruments 
are  employed.  These  are  electrically  locked  and  equipped  with 
a  handle,  the  turning  of  which  will  make  and  break  electrical 
contacts.  !;<>r  the  locking  and  unlocking  of  the  switch  lock,  tower 
instruments  should  be  locked  full  normal  and  full  reverse :  full 
normal  to  prevent  the  instrument  from  being  operated  after  a 
high  speed  signal  is  cleared,  as  the  reversal  of  the  instrument 
may  place  a  signal  at  danger  after  having  been  accepted  by  an 
approaching  train ;  full  reverse  to  prevent  the  release  of  the 
instrument  unless  the  switch  and  the  switch  lock  are  in  their 
proper  normal  positions.     In  Fig.  200  lock  magnet  A  on  tower 

192 


OUTLYING   SWITCH   LOCKING 

instrument  is  normally  de-energized  and  the  commutator, 
operated  by  the  handle,  can  be  given  a  predetermined  preliminary 
movement,  just  enough  to  make  contact  1  provided  signal  lever 
1  is  in  the  normal  position.  The  lock  armature  picking  up  will 
permit  further  movement  of  the  handle  to  take  place,  which,  in 
turn,  will  break  contact  2  and  make  contact  4.  Contact  1  is 
used  for  the  control  of  signal  1  and  contact  3  for  the  cross-pro- 
tection of  this  signal  when  the  tower  instrument  is  reversed. 
Contact  4  is  employed  for  the  control  of  the  switch  lock  while 
contact  5  completes  a  cross-protection  contact  when  the  tower  in- 
strument is  normal.    The  contact  15  on  lever  1  provides  cross-pro- 


DJ 


f~TJ1      B 


FIG.  200. 


tection  for  tower  instrument  lock  magnet  when  this  lever  is  re- 
versed. Previous  discussion  of  the  switch  lock  control  and  in- 
dicating features  should  be  sufficient  and  no  further  comments 
necessary.  Neither  should  the  arrangements  for  other  types  of 
switch  locks,  as  controlled  from  a  tower  instrument,  need  fur- 
ther comments.  It  should  be  observed  that  in  all  cases  the  cross 
protection  contacts  must  break  before  the  contro  contacts  make 
otherwise  the  battery  will  be  short  circuited  during  the  operation 
nf  the  lever. 

At  Power  Plants.  At  power  interlockings,  in  addition  to 
the  employment  of  regular  switch  locks  and  previously  discussed 
circuit  arrangements,  dwarf  signal  mechanisms  of  the  solenoid 
type  or  other  specially  designed  high  voltage  devices  are  often 
installed.  These  mechanisms  are  controlled  through  regular  in- 
terlocked levers  and  the  same  method  of  indication  at  the  lever 
provided  as  that  arranged  with  the  other  levers  in  the  same 
system.     Of  course   the   normal   position   of  the   lever   will    lock 

193 


ELECTRIC    LOCKING 


the  switch  and  the  reverse  position  will  unlock  it.  Hence,  the 
indication  for  the  corresponding  position  of  the  lever  and  the 
switch  should  be  reverse  of  that  of  a  signal  lever  indication. 

Communicating  Devices.  In  connection  with  outlying  >witch 
locking,  some  means  of  communication  must  be  maintained  be- 
tween the  switch  and  the  tower  from  which  it  is  controlled. 
Bells  and  a  bell  code  are  often  employed  for  this  purpose,  the 
circuit  being  arranged  as  shown  in  Fig.  201  by  the  means  of  one 

AT  Tower.  At  Switch 


li-. 


B+ 


FIG.  201. 

wire.  A  hand  switch  located  at  the  switch  and  one  in  the  tower 
will,  when  either  is  depressed,  ring  the  bell  at  the  opposite  end. 
This  method  of  arranging  a  bell  circuit  is  often  installed  be- 
tween adjacent  towers.  A  telephone  used  as  a  communicating 
medium  will  be  found  much  more  satisfactory  for  the  use  of 
trainmen,  as  it  is  frequently  necessary  to  hold  a  conversation 
totally  beyond  the  capacity  of  a  bell  code.  With  a  telephone 
attachment  a  condenser  is  generally  employed.  As  an  alternat- 
ing current  is  used,  this  permits  condensers  to  be  inserted  with- 
out interfering  with  the  operation  of  the  circuits.  Hence  a  di- 
rect current  common  or  an  operating  wire  used  in  the  opera- 
tion or  indication  of  a  switch  locking  circuit  can  also  be  used 
for  a  telephone  circuit.  An  arrangement  of  this  kind  is  shown 
in  Fig.  202,  in  which,  as  is  usually  the  case,  a  ground  return  is 


At  Tower 


At  switch 


I 

' 

V 

> 

n 

COM*\Ols| 

t 

i^ 

FIG.  202. 


used  for  the  telephone.  It  will  be  noted  that  on  account  of  the 
condenser  no  direct  current  can  pass  from  the  lock  circuit  to  the 
ground. 

194 


XII 

BRIDGE    LOCKING 

General.  Bridge  locking  is  that  class  of  electric  locking 
where  draw-bridges  or  other  types  of  movable  bridges  arc 
locked  in  their  closed  position,  and  so  interlocked  with  the  signals 
approaching  the  bridge  that  they  cannot  be  cleared  unless  the 
bridge  is  locked  in  its  properly  closed  position.  This  can  be 
accomplished  in  various  ways,  and  should  not  only  include  the 
interlocking  of  such  levers  in  the  interlocking  machine  as  directly 
or  indirectly  control  the  bridge  and  signals  protecting  the  bridge, 
but  also  provide  the  locking  of  other  parts  of  the  bridge,  the 
proper  position  of  which  is  important  to  the  safe  passing  of  trains. 
Hence,  bridge  locks,  rail  locks,  bridge  circuit  controllers,  bridge 
couplers  and  other  appliances  are  necessary  adjuncts  to  insure  the 
safety  of  train  movements  over  a  drawbridge. 

One  of  the  most  important  factors  of  drawbridge  locking  is  the 
provisions  that  must  be  made  to  prevent  any  attempt  to  put  in 
motion  the  movable  parts  of  a  bridge  unless  all  derails  and 
signals  protecting  the  bridge  are  in  their  normal  position.  Pro- 
visions for  the  locking  of  the  drawbridge  are  not  sufficient,  as 
the  bridge  operator  may  start  his  machinery  and  injure  the  bridge 
operating  parts,  because  the  bridge,  being  locked,  cannot  move ; 
or  it  may  result  in  the  breaking  of  the  bridge-locking  parts  and 
cause  the  opening  of  the  draw.  The  means  and  schemes  employed 
in  preventing  the  operation  of  a  bridge  when  it  is  locked  and  in 
locking  the  bridge  after  it  is  unlocked  will  depend  very  much 
upon  the  type  of  control  and  manner  of  operation  of  the  bridge. 

Bridge  Engine  Control.  Where  a  bridge  is  operated  by  a 
steam  or  gasoline  engine  some  mechanical  means  are  generally 
provided  to  prevent  the  starting  of  the  bridge  operating  machin- 
ery. This  is  generally  accomplished  by  employing  a  lever  in  the 
interlocking  machine  to  lock  the  engine  which  puts  the  movable 
parts  of  the  drawbridge  into  motion  so  that  it  cannot  be  started 
when  the  lever  is  reversed.  By  having  this  lever  operate  an 
ordinary  bolt  lock  or  a  facing  point  lock,  which  is  connected  to  the 
lever  of  the  engine,  the  engine  will  be  under  the  direct  control 
of  what  is  generally  called  the  "starting"  or  "bridge-lock  lever" 
in  the  interlocking  machine.     By  having  all  other  levers  in  the 

195 


ELECTRIC   LOCKING 

machine  lock  this  lever  reversed,  either  directly  or  indirectly, 
no  other  lever  can  be  reversed  until  the  engine  is  cut  out,  and 
the  engine  cannot  be  started  again  until  all  levers  are  normal. 
The  engine-operating  lever  can  of  course  also  be  locked  electrically 
by  an  electric  lock,  preventing  its  release  unless  energized.  It 
is  desirable  to  also  have  the  bridge  itself  locked  in  position  by 
mechanical  bridge  locks  operated  from  the  interlocking  machine. 

Bridge  -Motor  Control.  When  the  bridges  are  electrically 
operated  the  electrical  control  wires  may  be  broken  through  the 
starting  lever  or  the  bridge  lock  lever  when  normal,  so  that 
with  this  lever  reversed  the  bridge  operator  will  be  unable  to 
start  the  bridge  machinery.  It  may  also  be  accomplished  by 
means  of  a  relay  so  controlled  that  when  the  bridge  is  unlocked 
it  will  become  energized,  and  the  bridge  control  circuit  broken 
through  this  relay. 

Special  Devices.  Draw  and  lift  bridge  protection  necessitates 
the  use  of  various  special  devices  to  insure  the  correct  position 
of  the  draw  span  and  the  rails,  and  to  insure  the  completion 
of  circuits  and  pipe  lines  over  the  bridge.  Among  these  are 
bridge  locks,  rail  locks,  bridge  circuit  controllers  and  bridge 
couplers. 

Bridge  Locks.  There  are  numerous  devices  and  methods  used 
for  the  purpose  of  locking  a  draw  or  lift  bridge  in  its  closed 
position.  Many  of  these  devices  are  specially  designed  for  the 
particular  type  of  bridge  to  which  they  are  to  be  applied.  All 
bridge-locking  appliances  should  be  designed  to  lock  the  bridge 
only  when  the  draw  is  in  the  proper  position,  both  with  respect  to 
its  vertical  and  horizontal  alignment. 

With  the  so-called  gravity  bridge  lock,  the  bridge  is  locked  by 
a  plunger  which  passes  through  holes  in  two  castings,  one  of 
which  is  attached  to  the  bridge  and  the  other  to  the  bridge 
abutment.  The  locking  of  a  bridge  can  also  be  accomplished 
with  a  bolt  lock,  designed  on  the  same  principle  as  an  ordinary 
bolt  lock.  The  tappet  which  corresponds  with  the  lock  bar  on 
an  ordinary  bolt  lock  is  moved  by  the  bridge-operating  lever  and 
locked  by  the  plunger,  which  is  operated  from  the  interlocking 
tower.     An  F,   1'.  L.  attached  to  the  bridge  shoe  is  occasionally 

196 


BRIDGE   LOCKING 

used.  Often,  in  conjunction  with  a  bridge  lock,  circuit  con- 
trollers are  attached  to  the  structure,  which  closes  a  circuit 
when  the  draw  is  in  its  proper  position.  In  addition  thereto,  an- 
other circuit  controller,  which  insures  the  proper  position  of  the 
wedges  supporting  the  draw  ends,  will  close  a  circuit  and  a  lever 
lock  on  the  bridge  lock  lever  controlled  in  series  through  these 
controllers. 

Rail  Locks.  The  lifting  or  spreading  rails  at  the  ends  of 
draw  and  lift  bridges  must  be  locked  to  insure  their  being 
properly  located  for  a  train  movement.  A  locking  device  of  this 
nature  must  be  applied  to  all  rails  to  insure  each  rail  being  in 
position  and  properly  placed  before  a  signal  can  be  cleared  for 
train  movements  over  the  bridge.  The  rail  ends  of  a  drawbridge 
are  often  treated  as  switches  and  locked  with  F.  P.  L.'s  of  a 
design  and  construction  much  heavier  than  those  used  for 
switches.  Locking  cams  and  slide  bars  are  used  to  a  great  extent 
for  the  proper  alignment  of  the  rails.  Where  locking  cams  are 
employed  rail  dogs  are  actuated  by  the  rails  when  they  assume 
their  proper  place  and  are  locked  by  cams  operated  from  the  inter- 
locking machine.  Slide  bar  arrangements  are  on  the  same 
order  as  F.  P.  L.'s. 

Bridge  Circuit  Controllers.  Where  it  is  necessary  to  carry 
circuits  onto  or  across  drawbridges,  bridge  circuit  controllers 
are  employed  to  disconnect  the  circuits  when  the  draw  is  open 
and  again  connect  them  when  the  draw  is  closed.  The  circuit 
controllers  are  operated  by  mechanical  connections  and  generally 
attached  to  some  other  bridge-operating  or  bridge-locking  parts, 
such  as  the  rail  or  bridge  lock.  As  a  rule,  the  track  circuit  is 
connected  through  the  circuit  controllers,  thereby  de-energizing 
the  track  relay  when  the  draw  is  open.  Other  circuits,  which  it 
is  desirable  to  break  when  the  draw  is  open,  can  be  carried 
through  these  controllers.  The  contacts  are  constructed  and  ar- 
ranged so  as  to  provide  for  considerable  lateral  and  vertical 
misalignment  and  end  play  of  the  bridge  with  the  fixed  abut- 
ments or  shore. 

Hridge  Coupler.  A  bridge  coupler  is  a  device  used  for  con- 
necting or   disconnecting   the   pipe    runs   between   the   approach 

197 


ELECTRIC    LOCKING 


and  swing  spans  of  a  drawbridge  where  the  continuity  of  the 
pipe  runs  is  broken  when  the  bridge  is  opened.  The  coupler 
consists  of  two  sections,  one  of  which  is  placed  on  the  draw 
span,  while  the  other  is  placed  on  the  approach  side. 

Interlocking  Arrangement.  The  movement  of  trains  over 
draw  or  lift  bridges  is  generally  protected  by  signals  operated 
from  one  interlocking  machine.     Fig.  203  shows  a  typical  draw- 


RA\ilocns4- 


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RwlLocks4- 

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11 


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DravmBRid&E 


COUPLER  5 


COUPLER  5 


starting  lever  or 
Bridge  Lock  Lever   €> 


FIG.   203. 


Locking. 

3  x  ® 

*  x   ® 
5X    ® 

io  x  (§) 


bridge  layout  for  a  mechanical  interlocking.  It  will  be  noted 
that  in  addition  to  the  levers  required  for  the  derail,  F.  P.  L. 
and  signals,  a  rail  lock  and  coupler  lever  is  employed.  Further- 
more, one  lever  is  functioned  as  a  starting  or  bridge-locking  lever 
to  lock  and  unlock  the  bridge  operating  machinery.  Levers  so 
functioned  are  interlocked  with  the  operating  mechanism  of 
the  drawbridge,  making  it  impossible  to  operate  the  draw  until 
it  is  placed  normal.  The  bridge-locking  lever  when  normal  will 
permit  the  draw  to  be  opened,  but  the  lever  cannot  again  be 
reversed  until  the  draw  is  closed.  Hence,  in  a  layout,  as  shown 
in  Fig.  203,  the  restoration  to  normal  of  lever  6  will  directly 
or  indirectly  lock  all  derails  in  their  normal  position.  Conse- 
quently, before  the  draw  can  be  opened,  all  derails  must  be  locked 
in  a  position  to  derail  approaching  trains  that  do  not  observe  the 
signal  indications. 

At  mechanical  interlockings  installed  for  the  protection  of  a 
drawbridge  it  is  always  most  desirable  to  operate  the  facing 
point  locks  and  derails  on  each  side  of  the  tower  with  a  separate 
lever  as  this  will  insure  easier  and  safer  operation  and  main- 
tenance. It  is  also  desirable,  in  most  cases,  to  operate  the  couplers 
and  rail  locks  at  each  end  of  the  draw  with  separate  levers.  This 
is  particularly  true  where  the  tower  is  not  located  on  the  draw- 

198 


BRIDGE    LOCKING 

bridge.  Separate  levers  for  the  couplers  will  be  necessary  because 
the  pipe  lines  at  the  tower  end  of  the  draw  should  be  coupled 
before  a  through  connection  can  be  obtained  to  operate  the 
coupler  at  the  other  end  of  the  draw.  Furthermore,  it  is  desirable 
to  lock  the  rails  at  one  end  of  the  draw  before  the  connections  are 
coupled,  and  to  accomplish  this  the  rail  locks  must  be  operated 
from  separate  levers. 

At  some  interlocking  plants  the  arrangement  is  as  shown  in 
Fig.  204.     Here  rail  locks  and  bridge  locks  only  are  used,  the 


Raillock  5 


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Bridge  Lock 3 


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7  A  ©© 


FIG.    204. 


bridge  locks  being  applied  to  the  bridge  proper  and  the  bridge- 
operating  protection  provided  by  electrical  means.  The  inter- 
locking will  insure  that,  before  the  bridge  is  unlocked,  the  derails 
must  be  normal  and  the  rail  locks  withdrawn.  Conversely,  the 
rail  locks  cannot  be  reversed  until  the  bridge  is  locked,  and  the 
derails  cannot  be  reversed  until  the  rails  are  properly  locked. 


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Circuit  Arrangements.  An  electric  arrangement  of  locking 
an  engine  lever,  where  the  interlocking  is  located  on  the  shore  end 
and  the  bridge-operating  room  on  the  bridge,  is  shown  in  Fig.  205. 
When  starting  lever  6  normal  plunger  lock  A,  which  locks  tappet 
bar  attached  to  lever  controlling  throttle  of  bridge  engine  D,  will 

199 


ELECTRIC    LOCK  IXC 

be  energized.  An  indication  lock  B  on  lever  6  will  release  this 
lever  only  when  the  engine-controlling  lever  is  normal  and  the 
rail   lock   in   the   proper   position.      Fig.   206  illustrates   another 

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FIG.   206. 

method,  in  which  circuit  controller  A  closes  automatically  only 
when  the  draw  is  in  proper  position  and  B  closes  automatically 
when  the  wedges  supporting  the  draw  ends  are  in  the  proper 
position.  This  will  energize  relay  X,  which  controls  the  signals, 
bridge  and  rail  locks.  Circuit  controller  D  closes  when  the  bridge 
and  rail  locks  are  withdrawn  by  these  levers  being  placed  normal 
and  this  circuit  will  energize  indicator  Y  in  the  bridge-operating 
room  and  complete  the  bridge  control  circuit. 

One  scheme  of  an  electrical  locking  arrangement  of  a  complete 
drawbridge  protection  is  shown  in  Fig.  207.     It  will  be  observed 


RL.5 


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B.L.3 


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FIG.   207. 


that  the  bridge  operating  release  circuit  breaker  is  controlled 
through  relay  A  and  this  relay  can  only  be  energized  by  the  normal 
position  of  all  derails,  bridge  and  rail  locks.  In  order  to  clear  a 
signal  the  circuits  are  so  arranged  that  this  can  only  be  accom- 
plished by  the  locking  of  all  devices  in  proper  sequence.  The 
arrangement  insures  that  the  derails  cannot  be  reversed  and  the 
signals  cleared  unless  the  rail  locks  are  reversed.  The  unlocking 
of  the  bridge  can  only  take  effect  by  the  rail  locks  being  placed 

200 


BRIDGE    LOCKING 

normal;  this  can  only  be  done  if  the  derails  are  normal,  and  the 
bridge  lock  can  only  be  placed  normal  after  the  rail  locks  are 
normal.  The  derails  are  equipped  with  normal  and  reverse  locks, 
which  are  controlled  through  the  track  circuits  and,  if  desired, 
through  route-locking  mediums.  As  the  opening  of  the  draw  will 
de-energize  the  track  relays,  the  derails  will  be  locked  in  their 
normal  position  as  an  additional  protection  against  their  reversal 
during  the  operation  of  the  bridge. 

Another  scheme  of  bridge-locking  protection  is  shown  in  Fig. 
208.     Here  relay  A  is  controlled  through  normal  contacts  on  the 


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levers   2-7 


FIG.  208. 


derails  and  the  rail  and  bridge  locks  controlled  through  a  front 
point.  Relay  \)  is  controlled  through  normally  closed  contacts, 
the  bridge  and  rail  locks  when  these  are  normal,  and  through  a 
front  point  of  relax  A  and  a  back  point  of  relax'  C.  This  relax 
controls  an  indicator  in  the  bridge-operating  room  (generally 
provided  where  the  bridge-operating  room  is  located  away  from 
the  interlocking  tower)  and  the  indicator  controls  the  bridge- 
operating  circuit  breaker.  Relay  C  is  controlled  through  reverse 
contacts  on  the  rail  and  bridge  locks,  and  a  back  point  of  relay  B. 
This  relay  controls  the  operation  of  derails  2  and  7.  In  this  wax 
a  complete  indication  as  to  the  proper  position  and  operation  of 
all  devices  is  procured,  thereby  insuring  a  mechanical  as  well  as 
electrical  interlocking  of  all  apparatus  used  in  the  protection  of 
trains  for  movements  over  the  bridge.  At  power  interlockings 
where  all  bridge  and  rail  locking  is  operated  by  switch  or  dwarf 

201 


ELECTRIC    LOCKING 

mechanism  additional  protection  is  provided  by  the  indication  that 
is  given  by  such  mechanisms  to  insure  a  corresponding  position 
of  the  function  and  the  lever  by  which  it  is  controlled.  Circuit 
arrangements  can  also  be  made  where  two  individual  bridge  locks 
for  each  bridge  are  provided,  one  controlled  from  the  interlocking 
machine  and  the  other  from  the  bridge-operating  room,  when  the 
bridge-operating  room  bridge-lock  is  controlled  through  contacts 
on  the  interlocking  bridge  lock  as  shown  in  Fig.  209.     Hence  the 


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FIG.  209. 

bridge  cannot  be  unlocked  until  a  release  is  obtained  from  the 
leverman  in  the  tower  by  his  operation  of  the  interlocking  bridge 
lock  lever. 

Arrangements  are  also  in  use  where  contacts  on  the  bridge 
lock  lever  in  the  interlocking  machine,  when  this  lever  is  nor- 
mal, will  complete  the  bridge  operating  circuit. 

Track  Circuit.  At  draw  or  lift  bridges,  where  track  circuits 
are  employed  for  electric  locking  or  other  purposes,  it  is  always 
desirable  to  continue  these  through  the  rails  across  the  bridge  so 
that  no  dead  section  will  be  present  in  the  track  circuit  protection. 
The  rails  across  the  bridge  can  be  cut  out  of  the  track  circuit. 
Submarine  cables  are  often  employed  to  complete  the  track  circuit 
between  both  drawbridge  abutments,  but  this  is  not  advisable  as 
submarine  cables  are  not  only  very  costly,  but  such  an  arrange- 
ment does  not  break  the  track  circuit  when  the  bridge  is  open, 
nor  does  it  give  proper  track  circuit  protection  against  broken 
rails,  etc.  A  circuit  breaking  device  operated  coincidently  with 
the  movement  of  the  bridge  is  an  advisable  feature  to  employ. 
Hence  the  most  general  and  safest  way  of  arranging  a  draw- 
bridge track  circuit  is  to  maintain  a  circuit  through  the  rails  of 
the  bridge  by  means  of  two  or  more  bridge  circuit  controllers. 
These  controllers  are  either  operated  by  the  same  lever  that  moves 

202 


BRIDGE    LOCKING 

the  bridge-lock  which  locks  the  bridge  in  its  closed  position,  or 
the  lever  operating  the  rail-locks  which  locks  the  rails  in  their 
proper  alignment,  the  arrangement  depending  upon  the  scheme 
of  electric  locking  protection.  They  can  also  be  operated  by  a 
separate  lever  which  can  be  moved  only  after  the  bridge  is  set 
and  locked  in  its  normal  position.  At  mechanical  interlockings 
they  can  be  operated  in  conjunction  with  the  pipe  coupler,  which 
couples  and  uncouples  the  pipe  lines  extending  over  the  bridge. 


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FIG.  210. 


Fig  210  shows  a  track  circuit  carried  across  a  drawbridge  by 
means  of  two  bridge  circuit  controllers  A  and  B.  It  will  be  noted 
that  insulated  joints  C  are  placed  in  each  rail  at  both  ends  of  the 
bridge  and  at  the  end  of  the  pier  tracks.  While  this  is  not  always 
necessary  it  is  a  very  commendable  practice  as  it  will  tend  to 
simplify  the  insulating  of  other  parts  of  the  bridge,  which  may 
often  become  quite  complicated.  Jumpers  from  each  rail  are 
connected  to  the  respective  sides  of  the  bridge  circuit  controllers. 
half  of  each  controller  being  located  on  the  piers  and  half  on  the 
bridge.  At  places  where  no  continuous  track  circuit  can  be  main- 
tained the  installation  of  a  trap  circuit  arrangement  is  recom- 
mended. There  are  drawbridges,  however,  where  no  track  circuit 
can  be  maintained,  due  to  the  employment  of  steel  ties  or  bridges 
which,  beim;  built  of  steel,  are  constructed  so  as  to  receive  the  rails 
without  the  intervening  wooden  ties.  In  such  cases  there  is  no 
alternative  but  to  leave  the  bridge  a  dead  section  by  placing  in- 
sulated joints  at  each  end  of  the  piers  and  joint  the  rails  with 
jumpers  placed  in  a  submarine  cable.  In  this  way  the  entire  bridge 
will  constitute  a  dead  section.  The  installation,  therefore,  of  some 
type  of  a  trap  circuit  is  to  be  recommended. 


203 


XIII 

TESTING 

General.  There  are  a  number  of  very  essential  tests  that 
should  be  conducted  both  before  and  after  an  electric  locking 
protection  is  put  in  service  at  an  interlocking  plant.  The  indica- 
tion magnets,  lever  locks,  relays  and  other  magnetic  safety  appli- 
ances should  be  checked  out  to  determine  the  pick-up  and  drop- 
away  values,  resistance  of  coils  and  contact  resistance  of  all  points. 
This  should  be  done  before  the  electric  locking  is  placed  into 
operation  or  actual  service,  since  it  is  more  convenient  to  do  so 
at  such  a  time,  and  allows  changing  out  any  defective  parts  or 
units  without  interfering  with  the  operation  of  the  plant.  Tests 
to  ascertain  the  safe  service  conditions  of  the  circuits  and  appli- 
ances should,  of  course,  be  conducted  at  frequent  intervals. 

INSTALLATION  TESTS. 

Method.  After  the  electric  locking  is  installed  tests  should 
be  made  to  insure  the  circuits  and  apparatus  being  properly  de- 
signed, applied  and  installed.  These  tests  should  be  made  before 
a  system  is  approved  and  put  in  service.  With  such  tests  it  is 
not  only  necessary  that  the  installation  be  checked  to  correspond 
with  the  circuit  plans,  but  a  thorough  test  should  be  made  to 
make  sure  that  the  desired  protection  has  been  fully  accom- 
plished. A  complete  knowledge  of  the  principles  of  the  electric 
locking  scheme  employed  is  essential  to  the  satisfactory  testing 
of  a  plant,  and  when  testing  the  circuits  conditions  should  be 
as  near  a  duplicate  of  the  regular  operation  of  a  circuit  during 
actual  service  as  circumstances  permit. 

A  good  method  of  testing  electric  locking  installations  is  to 
first  compile  a  chart  in  which  all  routing  of  trains  is  taken  care 
of  by  the  levers  being  manipulated  in  proper  sequence  and  in 
accordance  with  the  interlocking  in  the  machine.  This  method  is 
desirable  because  it  is  difficult  to  thoroughly  check  the  electric 
locking  for  a  complicated  track  layout  by  the  interlocking  plan. 
It  is  insufficient  to  conduct  a  test  by  trying  out  the  circuit  plan, 
as  errors  in  the  design  and  construction  can  only  be  found  by  a 
thorough  test  duplicating  the  ordinary  service  conditions. 

204 


TESTING 

Wiring.     Ii  is  required,  before  placing  wiring  in  service,  that 

the  wiring  of  each  circuit  be  tested  for  crosses,  grounds  and  con- 
tinuity of  the  circuit.  For  this  purpose  a  megger  or  magneto  is 
generally  employed.  The  testing  is  done  by  disconnecting  the 
wires  at  each  end  of  the  circuit  and  connecting"  the  testing  instru- 
ment between  the  wire  and  ground.  Where  a  common  return 
wire  is  employed  it  is  also  desirable  that  tbe  common  wire  be 
tested  for  grounds  unless  local  conditions  make  it  impossible 
to  keep  this  wire  entirely  free  from  grounds.  Tests  should  also 
be  conducted  by  connecting  the  testing  instrument  between  all 
wires  of  circuits  with  which  it  is  possible  for  the  circuit  being 
tested  to  be  crossed,  and  also  ring  out  each  complete  circuit  to 
ascertain  its  continuity.  A  detailed  check  of  all  wires  should  be 
made  to  verify  the  marking  of  the  tags  with  the  plans  and  to 
determine  whether  the  specification  for  the  installation  has  been 
complied  with. 

Relays  and  Indicators.  A  test  of  all  relays  and  tower  indi- 
cators should  be  made  to  see  that  the  RailwaySignal  Association's 
specifications  for  the  pick-up,  drop-away,  contact  opening  and 
armature  air  gaps  are  complied  with.  If  the  coils  of  a  relay  or 
indicator  are  changed  to  a  slightly  higher  or  lower  resistance, 
the  pick-up  and  drop-away  values  will  frequently  change  beyond 
the  required  limits,  in  which  case  the  armature  drop-away  or 
pick-up  air  gap  must  be  changed  until  tbe  correct  value  of  the 
points  is  readied  and  the  specifications  met.  If  the  contact  finger 
opening  of  the  relay  is  changed,  enough  spring  tension  must  be 
left  on  the  fingers  to  secure  sliding  contact  when  the  coils  are 
energized.  The  pick-up  and  release  test  of  indication  magnet 
coils  is  conducted  in  the  same  manner  as  tbe  relays.  When  tak- 
ing the  pick-up  of  tbese  magnets,  on  most  types  of  power  inter- 
lockings,  only  the  first  reading  should  be  considered,  and  if  an- 
other reading  is  necessary  the  lever  should  be  operated  before 
any  is  again  taken.  This  is  necessary  because  of  the  mechanical 
construction  of  tbe  indication  parts  on  the  lever,  which  will 
remain  in  a  released  position  after  once  being  actuated. 

Track  Circuits.  Track  relays  are  checked  by  shunting  each 
respective  track  section  to  determine  whether  the  relay  responds 
properly.     Track   repeaters   or   track   indicators  are  checked  by 

205 


ELECTRIC   LOCKIXC 

shunting  the  track  section  or  by  directly  dropping  the  track  re- 
lays to  determine  whether  the  repeater  relay  or  indicator  dupli- 
cates the  movements  of  the  track  relay.  All  track  and  fouling 
circuits  and  frog  bonding  should  be  checked.  A  test  with  a  volt- 
meter will  greatly  simplify  this  procedure,  and  all  fouling  circuit 
readings  should  be  taken  back  of  the  clearance  of  the  diverging 
route. 

Lever  Locks.  Notches  cut  in  the  levers  of  a  power  inter- 
locking machine  for  the  receipt  of  the  plungers  or  locking  dog 
must  be  tested  for  proper  clearance.  The  lever  must  first  be 
tested  for  clearance  for  every  combination  that  locks  it.  This  is 
accomplished  by  having  the  lever  in  question  locked  by  another 
lever  through  the  medium  of  the  mechanical  dog  locking.  Then 
the  lever  is  pulled  or  pushed  hard  in  either  direction  to  take  up 
all  lost  motion,  current  being  applied  to  the  lock  during  this 
operation.  After  all  lost  motion  is  taken  up  and  after  current  is 
cut  oft"  from  the  lever  lock  it  should  be  noted  whether  the  lock 
plunger  or  dog  rests  into  the  notch  in  the  lever  or  whether  it 
rests  on  top  of  the  lever.  If  the  maintainer  is  unable  to  observe 
the  position  of  the  lock  plunger,  the  mechanical  locking  holding 
the  lever  under  test  should  be  released  and  an  attempt  made  to 
manipulate  the  lever  without  the  lever  lock  being  energized.  If 
this  can  be  done  it  shows  that  the  locking  plunger  did  not  drop 
into  the  notch  in  the  lever  and,  consequently,  the  notch  must  be 
cut  out  further  to  give  proper  clearance.  Generally  a  J/^-inch 
clearance  between  the  locking  plunger  and  the  edges  of  the  notch 
in  the  lever,  with  the  lever  in  the  locked  position,  is  required  for 
the  safe  operation  of  the  lock.  Repeat  the  test  for  other  locked 
positions  of  the  lever  and  for  every  combination  that  locks  it. 

On  mechanical  interlocking  machines  the  notches  cut  in  the 
locking  segments  of  the  lever  lock  for  the  receipt  of  the  plunger 
or  dog  on  the  electric  locks  must  be  tested  for  clearance.  This 
is  done  as  described  with  power  interlockings,  by  having  the  lever 
in  question  locked  with  another  lever  through  the  medium  of  the 
mechanical  dog  locking  and  then  raising  the  latch  handle  as  far 
as  possible,  thus  taking  up  all  lost  motion.  After  this  is  done, 
observe  the  position  of  the  locking  dog.  or  test  to  see  whether 
the  lever  will  unlock  with  the  lever  lock  de-energized.  Also  make 
tests  to  ascertain  whether  the  lever  lock  takes  effect  with  the 

206 


TESTING 

lever  in  the  proper  position.  To  conduct  such  a  test  the  proper 
line-up  of  levers  should  be  made  to  insure  the  lever  in  question 
being  released  by  the  mechanical  locking.  The  lever  should  then 
be  operated  with  current  cut  off  from  the  lever  lock  and  notice 
taken  of  the  travel  permitted  the  lever  or  the  lever  latch  with 
tbe  lever  lock  de-energized.  If,  for  instance,  the  latch  on  a 
mechanical  interlocking  machine  can  be  operated  more  than  one- 
quarter  its  stroke  from  the  latched  to  the  unlatched  position,  or 
from  the  unlatched  to  the  latched  position  (depending,  of  course, 
upon  when  the  lever  lock  is  to  be  effective)  the  lost  motion  effect- 
ing this  should  be  removed.  If  levers  on  power  interlockings 
can  be  operated  more  than  the  thickness  of  the  plunger  lock  or 
locking  dog  further  than  specified,  the  lost  motion  by  which  it  is 
effected  must  be  removed.  Also  make  tests  to  certify  all  current 
being  cut  off  the  lever  locks  when  the  lever  is  fully  normal  and 
reverse. 

Indication  Locking.  In  indication  locking  the  levers  should 
be  tested  for  lost  motion  in  mechanical  connections  as  well  as  for 
indication  lock  adjustment.  On  switch  levers  first  remove  the 
fuse  so  that  the  function  controlled  will  not  operate.  Then  re- 
verse the  lever,  noting  whether  it  stops  in  the  indicating  position, 
after  which  proceed  to  pick  the  indication  and  move  the  lever  to 
the  full  reverse  position.  Repeat  the  operation  while  moving  the 
lever  normal.  On  some  systems  of  interlocking  it  is  necessary 
t<>  have  the  switch  reversed  while  testing  the  normal  indication, 
and  vice  versa.  On  signal  levers  it  is,  of  course,  only  necessary 
to  test  for  normal  movement  of  the  lever.  On  other  types  of 
signals  it  is  necessary  to  disconnect  the  indication  wire  at  the 
lever  in  order  to  prevent  an  indication  being  received  at  the  lever. 

\\  here  levers  are  given  a  twisting  motion  during  the  operation, 
make  a  test  by  quickly  twisting  the  lever  with  considerable  force 
so  as  to  determine  whether  or  not  the  indication  latch  will  bound 
out  of  the  slots  or  quadrant.  When  testing  double  switch  levers 
test  each  one  separately.  Each  test-  should  be  repeated  four  times 
and  the  levers  operated  as  when  handled  by  the  leverman.  After 
each  lever  test  replace  the  wire  or  fuse  and  see  that  indication  is 
properly  received. 

The  next  test  will  be  to  ascertain  whether  a  function  will  indi- 
cate before  it  has  assumed  the  proper  position  for  the  safe  niove- 

207 


ELECTRIC  LOCKING 

ment  of  trains.  This  is  done  for  switches  by  inserting  a  test 
gauge  in  the  switch  point  and  noting  whether  the  switch  will 
indicate  on  any  gauge  larger  than  that  specified  as  standard  by 
the  road.  This,  of  course,  should  be  done  with  both  positions 
of  the  switch. 

For  signals  conduct  test  by  clearing  the  signal  and  noting  at 
what  angle  from  the  horizontal  position  of  the  semaphore  arm 
it  will  indicate.  This  can  readily  be  done  by  attempting  to  put 
the  lever  full  normal  while  the  arm  is  at  various  positions  and 
moving  toward  the  horizontal  position.  Another  method  is  to 
insert  an  ammeter  in  series  with  the  indication  circuit  and  observ- 
ing at  what  angle  of  the  signal  arm  the  needle  is  deflected. 

Test  indicators  on  3  pos.  signals  to  determine  that  a  double 
indication  is  not  received  while  the  signal  goes  from  the  90  to 
the  0-deg.  position.  It  should  be  impossible  to  release  the 
lever  when  the  signal  reaches  the  45-deg.  position,  as  the  signal 
might  stick  clear  in  this  position  and  an  indication  received. 

Section  Locking.  Test  section  locking  by  setting  up  routes 
for  the  various  train  movements  and  have  a  man  shunt  the  dif- 
ferent track  sections  within  the  interlocking  limits  while  the 
levers,  locked  by  these  track  relays,  are  tried  to  detemine  whether 
they  are  locked  in  their  proper  position.  If  the  track  indicator 
or  track  relay  becomes  de-energized  while  the  shunt  is  on  the 
track  and  it  is  impossible  to  release  the  levers  that  should  be 
locked,  the  section  locking  is  in  proper  order.  If  it  is  possible 
to  move  the  locked  lever,  the  lever  lock  may  be  out  of  adjustment 
or  the  indicator  or  track  relay  out  of  order,  and  readjustment 
should  be  made  immediately,  after  which  the  test  is  repeated. 

At  power  interlockings  where  section  locking  is  effective  by 
breaking  the  positive  control  wire  for  the  switches,  the  observa- 
tion of  whether  or  not  the  switch  takes  current  by  watching  the 
ammeter  is  sufficient.  If  no  ammeter  is  provided  the  switch  must 
be  watched  on  the  ground.  Test  all  lever  selections  and  com- 
binations of  the  section  locking  scheme  so  as  to  see  if  contacts 
are  broken  at  the  proper  time  and  that  proper  contact  shunts  are 
provided  as  called  for.  The  facilities  made  for  parallel  train 
movements  is  a  particularly  important  feature. 

208 


TESTING 

Route  Lock  inc..  Route  locking  is  tested  by  setting  up  all 
possible  routes  at  a  plant  and  observing,  by  trying  the  locked 
levers,  whether  they  are  properly  locked.  Then  create  condi- 
tions similar  to  those  existing  when  a  train  is  actually  passing 
over  the  route,  and  note  whether  all  levers  equipped  with  locks 
are  retained  in  the  locked  position  until  the  train  is  on  the  re- 
lease section  or  track  instrument,  or  passed  out  of  these.  All 
possible  conditions  that  the  installation  of  the  route  locking  is 
intended  to  obviate  should  be  tested.  For  example,  if  the  route 
locking  should  not  be  released  unless  the  signal  is  placed  normal 
while  the  train  is  occupying  the  route,  this  should  be  tested.  It 
should  be  evident  that  route  locking  must  be  tested  for  opposing 
train  movements  on  all  routes. 

While  a  route  is  locked  up  it  is  also  desirable  to  try  all  levers 
that  should  not  be  locked  to  make  certain  that  errors  in  the  cir- 
cuits have  not  been  made  which  will  tie  up  parallel  lining-up  of 
routes. 

Stick  Locking.  In  stick  locking  installations,  test  the  lock- 
ing by  first  setting  up  the  routes  to  which  the  scheme  has  been 
applied.  Where  the  stick  locking  takes  effect  with  the  clearing 
of  the  signal  arm  only,  reverse  the  signal  lever  and  clear  the 
signal  to  about  5  deg.  from  the  horizontal  and  then  quickly  place 
the  lever  normal.  This  is  done  to  insure  that  the  locking  is 
effective  with  only  a  partial  clearing  of  the  signal  and  to  prevent 
the  release  of  the  locking  unless  the  signal  has  assumed  the  stop 
position.  After  it  is  ascertained  that  the  locking  has  taken  effect 
by  noting  the  position  of  the  stick  relay  and  trying  the  locked 
levers,  effect  the  release  as  with  a  regular  train  movement.  If 
the  locking  is  effective  with  the  reversal  of  the  signal  lever,  pull 
this  lever  far  enough  to  break  the  cross-protection  contact  on  the 
normal  contact  of  the  lever;  or,  if  a  mechanical  signal,  just  raise 
the  latch  and  the  locking  should  then  take  effect.  The  circuit 
should  be  arranged  to  take  effect  with  only  a  partial  reversal  of 
the  lever  in  order  to  prevent  the  stick  locking  from  failing  to 
take  effect  if  a  signal  should  partly  clear  as  soon  as  the  cross- 
protection  contact  is  broken,  which  might  be  caused  by  a  cross 
on  the  control  wire.  Next  test  the  levers  and  release  the  locking, 
as  previously  discussed.  It"  the  stick  locking  breaks  through  two 
signal  circuit  controllers  in  scries  and  if  only  one  is  controlled 

209 


ELECTRIC   LOCKING 

from  a  lever  contact  as,  for  instance,  a  home  and  a  distant  signal, 
clear  the  home  signal  as  described.  The  distant  signal  will  not 
clear  because  the  home  signal  has  only  partly  moved  from  the 
normal  position.  This  will  check  the  home  signal  circuit  breaker. 
Then  take  a  jumper  and  shunt  around  the  home  signal  circuit 
breaker ;  clear  the  home  signal,  which  will  also  clear  the  distant 
signal,  and,  if  the  stick  locking  takes  effect,  it  is  a  sure  sign 
that  the  locking  is  also  controlled  by  the  distant  signal.  Another 
method  is  to  move  the  distant  arm  to  clear  by  hand  while  home 
signal  is  at  danger.  Where  many  levers  in  series  control  the 
stick  locking,  reverse  each  lever  successively  and  note  whether 
the  locking  takes  effect  with  each  lever  reversal. 

Approach  Locking.  First  test  the  approach  indicator  to  see 
that  it  indicates  the  approach  of  a  train  when  the  train  is  at  the 
proper  distance  from  the  tower  or  the  home  signal.  Then  set  up 
the  routes  to  which  approach  locking  is  applied  and  observe,  by 
dropping  the  approach  indicator,  whether  the  locking  is  effective 
with  this  indicating  the  approach  of  a  train.  Also  ascertain  by 
test  that  the  locking  does  not  take  effect  if  no  train  is  approach- 
ing. Then  try  the  locked  levers  and  release  the  locking  in  the 
same  manner  as  when  a  train  passes  over  the  route. 

Sectional  Route  Lock  inc.  In  sectional  route  locking  line 
up  the  complete  routes  for  train  movements  and  with  the  signal 
at  clear  try  all  levers  to  see  whether  they  are  properly  locked. 
Then  drop  all  track  relays  in  successive  order  and  try  if  all  levers 
controlling  the  switches  and  derails  ahead  of  the  train  are  locked 
up  and  if  all  the  switches  in  the  section  just  passed  by  the  train 
are  released.  Tests  should  be  conducted  for  every  possible  com- 
bination of  movements  and  routes  which  can  be  set  up  for  trains. 
Try  the  levers  that  should  not  be  locked  by  the  route  locking  of 
one  route  to  see  that  non-conflicting  line-up  of  routes  can  be  made. 

Check  Locking.  In  check  locking  one  man  at  each  tower 
between  which  the  protection  is  applied  should  be  in  constant 
communication  with  another.  Test  the  locking  by  arranging  the 
locking  and  unlocking  of  the  protection  as  with  regular  train 
movements.  While  the  locking  is  in  effect  all  track  sections 
which  will  affect  the  check  locking  between  the  towers  should  be 

210 


TESTING 

shunted  and  circuit  controllers  on  signals,  if  they  also  control 
the  locking,  should  be  tested  to  insure  the  complete  protection 
being  provided. 

Emergency  Releases.  In  all  types  of  locking  it  is  evident 
that,  where  emergency  releases  or  other  methods  of  releasing 
are  employed,  they  should  be  reversed  or  actuated  in  order  to 
determine  whether  this  part  of  the  circuit  is  in  correct  working 
order.  While  the  release  is  reversed  also  try  such  levers  or 
apparatus  that  should  be  locked  during  the  operation  of  the  re- 
lease. Always  note  that  it  takes  the  specified  length  of  time  to 
actuate  the  release,  as  this  is  of  much  importance. 

Time  Locks.  Mechanical  time  locks  attached  to  an  interlock- 
ing machine  should  be  tested  to  see  that  they  release  after  the 
specified  time  lapse;  and  also  that  the  mechanical  locking,  if  such 
is  connected  with  them,  is  performing  its  function  properly. 
Hand  operated  time  locks  should  be  manipulated  and  tested  for 
correct  time  operation. 

Screw  Releases.  Test  for  the  shortest  possible  time  required 
to  operate  them.  Note  whether,  as  soon  as  the  release  is  started 
from  its  normal  position,  the  circuits  controlled  through  the 
normal  contacts  are  broken  and  also  that  the  reverse  contacts  are 
not  made  until  a  complete  reversal  of  the  release  has  taken  place. 

Annunciators.  Test  annunciators  by  shunting  the  track  sec- 
tion by  which  they  are  actuated.  Also  note  whether  cut-out 
switches  or  other  circuit  arrangements  provided  for  the  cutting 
out  of  the  annunciator  have  the  proper  effect. 

(  )i  ri.vixo,  Switch  Locking.  Test  the  lock  at  the  switch  to 
see  if  it  can  be  unlocked  without  a  release  from  the  tower.  The 
lock  in  the  tower  should  be  tested  to  see  if  it  can  be  released 
before  the  switch  is  completely  locked.  Where  switch  point  pro- 
tection is  also  provided,  test  to  find  out  whether  the  lock  in  the 
tower  will  release  with  a  point  gauge  inserted  in  the  switch  point. 

Bridge  Locking.  Test  all  apparatus  and  circuits  to  see  that 
they  take  effect  and  accomplish  their  purpose  at  the  proper  time 
and  in  a  correct  manner. 

211 


ELECTRIC  LOCKING 
SERVICE  TESTS 

In  addition  to  installation  tests  as  just  described,  it  is  necessary 
to  conduct  service  tests  at  frequent  intervals  to  ascertain  that 
the  apparatus  and  circuits  continue  to  give  the  protection  and 
perform  the  function  for  which  they  were  installed.  These 
tests  are  conducted  along  the  same  lines  as  the  previously 
described  installation  tests,  although  in  many  cases  it  is  not 
necessary  to  make  them  as  rigid  and  thorough.  It  should  be 
observed  during  such  tests  that  no  tests  or  adjustments  which 
might  cause  detentions  to  train  movements  should  be  made  until 
information  has  been  received  relative  to  approaching  trains. 
The  handling  of  levers  during  tests  should  be  done  by  the  lever- 
man  or  under  his  direct  supervision,  so  that  he  will  know  at  all 
times  the  position  of  the  levers.  As  an  example  on  the  frequency 
of  such  tests  it  can  be  stated  that  lever  locks  should  be  tested 
once  a  week  to  see  that  they  take  effect  properly.  This  is  gen- 
erally done  by  operating  the  locks  while  noting  that  the  plunger 
or  lock  dog  pick-up  and  drop  in  correspondence  with  the  closing 
and  opening  of  the  circuit  through  the  lock  coils.  A  monthly 
test  is  made  to  ascertain  the  proper  clearance  of  notches  and  to 
discover  badly  worn  parts,  which  may  be  the  cause  of  dangerous 
derangements.  Other  tests  are  either  conducted  semi-yearly  or 
yearly,  as  conditions  warrant. 


212 


XIV 

MAINTENANCE 

( rENERAL.  A  proper  and  systematic  method  of  maintenance 
depends,  in  regard  to  details,  upon  existing  conditions  to  which 
the  particular  system  is  subjected.  Each  system  or  installation 
may  have  its  weak  places  so  that  a  discussion  of  maintenance  can 
be  carried  on  only  in  a  general  way.  Where  circuits  and  devices 
are  in  service  for  electric  locking  purposes  it  is  of  utmost  im- 
portance that  they  should  perform  their  work  and  operate  in 
accordance  with  the  purpose  of  and  the  plans  used  in  the  installa- 
tion. It  is  generally  known  that  levermen,  accustomed  to  the 
check  and  restrictions  imposed  upon  them  by  the  employment  of 
electric  locking,  will  grow  careless  and  depend  principally  upon 
the  devices  and  locking  provided  for  the  safe  handling  of  inter- 
locking apparatus  and  traffic.  The  average  leverman,  for  instance, 
would,  if  he  could  contrive  to  do  so,  change  a  route  without  first 
manipulating  the  hand  screwr  release  and  probably  compliment 
himself  on  his  adroitness.  In  all  probability  he  would  forget  or 
perhaps  deliberately  neglect  to  notify  the  maintainer  that  the 
screw  release  was  out  of  order.  It  might  be  said  of  any  type 
and  scheme  of  electric  locking  or,  for  that  matter,  of  any  scheme 
of  signaling,  that  the  system  is  as  safe  as  its  maintenance.  All 
appliances  and  circuits  must  be  efficiently  maintained  so  as  to  con- 
tinue to  give  the  safe  service  that  its  installation  intended.  Hence 
failures  occurring  with  the  electric  locking  which  tend  to  create 
dangerous  conditions  should  be  a  cause  for  severe  discipline  and 
unless  the  maintainer  has  redeeming  qualities  his  services  should 
be  dispensed  with. 

Safety  Precautions.  It  is  of  first  importance  that  electric 
lucking  appliances  be  protected  from  any  tampering  or  any  opera- 
tion which  tends  to  beat  the  combination.  Such  an  operation 
might  happen  through  deliberate  action  on  the  part  of  the  lever- 
man  or  some  one  present  in  the  tower.  Deliberate  or  accidental 
action  to  this  effect  can  only  be  prevented  by  adequately  keeping 
under  lock  all  devices  that  should  not  be  accessible  to  the  leverman 
or  others.  If  this  is  not  done  there  are  no  restrictions  placed  on 
the  leverman  and  the  electric  locking  may  be  circumvented  with- 
out a  check  being  had  upon  such  action.    For  this  reason  all  com- 

213 


ELECTRIC   LOCKING 

partments,  interlocking  machine  cabinets  and  cases  enclosing 
circuit  controllers,  releases,  indicators,  relays,  etc.,  should  be 
properly  locked  at  all  times.  Nevertheless,  it  is  necessary  to  do 
something  in  case  of  a  derangement  of  apparatus,  otherwise  it 
would  be  impossible  to  change  a  route,  with  consequent  congestion 
and  delay  to  traffic.  Some  railroads  equip  all  devices  to  be  locked 
up  with  padlocks  and  provide  a  key  box  containing  the  key  for 
the  unlocking  of  such  apparatus  or  interlocking  machine  parts 
which,  in  an  emergency,  the  leverman  should  have  access  to. 
Such  boxes  are  equipped  with  a  glass  front  which  must  be  broken 
before  the  key  can  be  obtained.  The  leverman  is  kept  accountable 
for  such  breakage  and  must  record  on  the  daily  report  blank  the 
occasion  for  such  action.  The  key  box  should  be  so  constructed 
that  the  glass  can  readily  be  replaced  and  the  maintainer  must 
do  so  at  the  earliest  opportunity.  Glass  pieces  should  be  kept  on 
hand  for  this  purpose.  ( )n  some  railroads  devices,  instead  of 
being  locked,  are  sealed  with  a  car  seal  or  similar  article.  Then 
if  there  is  real  need  of  getting  access  to  the  sealed  part  the  lever- 
man can  break  the  seal,  open  the  case  and,  for  example,  "pick"  a 
lock.  It  is  obvious  that  sealing  irons,  seals,  etc.,  must  only  be  in 
possession  of  one  responsible  person  and  not  the  leverman.  In 
this  way  a  check  is  maintained,  as  in  the  case  of  the  glass  front 
box  or  broken  seal,  since  such  a  procedure  must  be  recorded.  It 
should  be  noted  at  least  every  morning  and  night  that  the  seals 
or  glass  are  intact.  In  case  the  leverman  fails  to  report  the 
necessity  of  breaking  into  the  apparatus,  when  getting  the  box  in 
order  again  it  should  be  noted  that  all  apparatus  is  properly  locked 
or  sealed. 

Failure  Emergency  Instructions.  In  case  of  failure  of  the 
electric  locking,  when,  for  instance,  it  fails  to  release  after  a  train 
has  passed  out  of  the  limits  of  the  locking  section,  the  leverman 
should  operate  the  emergency  release  or  the  hand  screw  release. 
If  this  has  no  effect,  note  whether  all  levers,  signal  arms  or  any 
apparatus  that  will  affect  the  electric  locking  are  in  their  proper 
positions,  after  which  again  actuate  the  release  medium.  If  this 
fails  to  release  the  electric  locking  the  maintainer  should  im- 
mediately be  notified.  If  it  is  necessary  to  operate  any  of  the 
locked  levers  before  the  maintainer  arrives  many  railroads,  in 
order  to  save  train  delays,  permit  the  leverman  to  release    the 

214 


MAINTENANCE 

lock  by  hand.  This  can  only  be  accomplished,  however,  after  the 
leverman  has  gained  access  to  the  key  which  unlocks  the  lever 
lock,  by  breaking  the  glass  of  the  key  box  or  by  breaking  the  seal 
placed  on  the  lock.  Before  unlocking  the  lever  lock  by  hand  the 
leverman  is  required  and  held  strictly  accountable  for  the  proper 
position  of  the  derail,  switch  signals  or  any  other  signal  appliance 
whose  lever  is  electrically  locked.  He  should  ascertain  that  the 
track  within  the  limits  of  the  locking  section  is  unobstructed  and 
that  no  car  is  standing  within  the  fouling  limits  of  the  track  cir- 
cuit. When  all  this  has  been  attended  to  the  lever  may  be 
operated.  With  regard  to  outlying  switch  locking  and  bridge 
locking,  failures  of  lever  locks  or  tower  instruments  should  be 
reported  to  the  maintainer  immediately  and  under  no  circum- 
stances should  the  leverman  operate  or  be  given  a  chance  to 
operate  such  locks  in  any  other  than  the  regular  manner. 

Inspection.  The  most  careful  inspection  and  frequent  service 
tests  of.  electric  locking  are  highly  justified,  as  a  careless,  excitable 
leverman  may  cause  serious  trouble  during  a  derangement.  It 
should  particularly  be  forcibly  impressed  upon  all  maintainers  that 
a  regular  inspection  as  well  as  testing  of  all  lever  locks  is  impera- 
tive to  the  safe  operation  of  a  plant.  Always  note  that  they  are 
properly  locked  and  sealed  ;  that  all  openings  are  closed,  allowing 
no  possible  chance  for  the  leverman  to  "pick"  the  lock  and  thereby 
circumvent  the  electric  locking.  Also  observe  that  the  lock  is 
securely  fastened  to  its  support  and  the  support  rigidly  attached  to 
the  machine.  Note  that  cotters  or  seals  on  pins  of  connecting 
rods  to  electric  locks  on  mechanical  interlockings  are  in  place  and 
intact ;  that  the  covers  are  properly  on  and  locked.  On  lever  cir- 
cuit controllers  see  that  the  contact  bands  and  strips  are  in  the 
proper  place ;  that  they  are  not  loose  or  have  slipped  out  of  their 
notches,  and  that  all  terminals  are  tight. 

During  inspection  take  cognizance  of  all  other  apparatus  con- 
nected with  the  electric  locking;  give  attention  to  the  relays, 
terminal  boards,  arresters,  etc.,  and  have  loose  nuts,  screws  and 
posts  tightened.  Inspect  time  locks  and  screw  releases,  etc.,  not- 
ing that  all  pins,  cotters,  bolts  and  nuts  are  in  place.  Also  examine 
batteries  to  see  if  exhausted  or  in  need  of  charging.  Observe  the 
operation  of  track  relays,  track  repeaters,  indicators  and  annun- 
ciators during  the  passing  of  trains  and  note  whether  they  operate 

215 


ELECTRIC   LOCKING 

quickly  and  properly.  Where  "SS"  relays  or  indicators  are  em- 
ployed, observe  that  they  open  and  respond  as  the  switches  change 
their  positions.  Make  tests  to  ascertain  the  effectiveness  of  the 
electric  locking  protection,  such  as  approach  locking  or  stick  lock- 
ing of  signals  and  advance,  route  or  section  locking  of  switches. 
Actuate  emergency  release  mediums  and  particularly  note  whether 
breaking  the  normal  contacts  has  the  proper  effect  upon  the  signal 
control  circuit  or  other  circuits.  On  tower  indicators  note  that 
glass  is  not  broken  and  that  they  are  properly  locked.  Indicators 
having  no  contacts  for  the  control  of  circuits  need  not  be  locked 
as  any  improper  operation  will  be  of  no  consequence  to  the  safety 
of  the  plant.  Emergency  switches  should  be  examined  to  make 
sure  that  they  are  placed  in  their  proper  position  and  that  the 
glass  covers  are  in  good  condition. 

Lever  Locks.  Lever  locks  and  particularly  solenoid  plunger 
lever  locks  should  be  thoroughly  cleaned  four  times  each  year. 
During  such  cleaning  all  gummed  substance  and  dirt  must  be 
thoroughly  wiped  away  and  removed  from  all  movable  parts  and 
journals  so  that  there  will  be  no  possibility  of  dirt  or  other  foreign 
substance  preventing  the  lock  from  dropping  by  gravity.  On 
solenoid  locks  the  plunger  and  brass  tube  inside  the  solenoid 
should  be  cleaned  in  a  similar  manner  with  a  dry  cloth.  On  all 
electric  locks,  and  lever  locks  in  particular,  it  is  of  utmost  im- 
portance that  the  lock  dog,  plunger  and  notches  in  the  lever  or  in 
the  lock  segment  have  perfectly  square  edges,  so  that  there  will 
be  no  possible  chance  for  the  lock  to  become  ineffective  and  cause 
a  dangerous  derangement  of  the  electric  locking.  When  re- 
cutting  or  enlarging  the  notches  in  levers  or  locking  dogs  for 
lever  locks,  always  see  that  the  corners  are  left  square  and  the 
surface  that  comes  up  against  the  lock  plunger  or  dog  vertical, 
thus  avoiding  a  tendency  to  force  the  lock  plunger  out  by  pulling 
hard  on  the  lever.  Each  lever  lock  should  be  tested  by  putting 
on  and  taking  off  current  several  times  to  ascertain  whether  it 
works  properly,  in  which  case  its  operation  should  be  quick  and 
sharp. 

When  enlarging  a  notch  in  a  lever  lock,  it  should  be  done  by 
chipping  with  a  light  hammer  and  small  cape  chisel,  being  careful 
to  prevent  the  chips  of  iron  from  getting  into  other  parts  of  the 
machine  or  locks. 

216 


MAINTENANCE 

When  the  cover  on  lever  locks  for  mechanical  interlockings  is  in 
place,  the  locking  clog  and  connecting  rod  to  it  are  completely 
covered,  which  prevents  any  tampering  with  them.  To  assist  in 
this  connection  a  shield  is  generally  secured  to  the  lock  bracket  to 
prevent  a  wire  or  tool  from  raising  the  locking  key  if  thrust  into 
the  hole  through  which  the  connecting  rod  extends.  Care  should 
be  used  when  replacing  covers  on  lever  locks  and  circuit  con- 
trollers, as  the  space  provided  for  wires  is  very  limited.  If  it 
should  happen  that  the  cover  rests  upon  an  insulated  wire  it  will 
result  in  the  insulation  wearing  off  and  cause  a  ground. 

Lexer  Indicating  Parts.  At  interlockings  where  the  lever  in- 
dicating parts  are  not  visible  it  should  be  a  general  practice  to 
remove  the  levers  from  the  machine  once  a  year,  together  with 
all  of  the  indicating  parts,  pins,  studs,  dogs,  springs  and  latches, 
all  of  which  arc  carefully  inspected  and  worn  or  broken  parts 
replaced.  It  is  particularly  important  that  all  sharp  edges  on  dogs 
or  other  parts  are  not  worn  round  or  changed  in  shape  or  size. 

In  testing  it  is  advisable  to  proceed  as  follows :  Select  a  lever 
and  guide  that  is  in  good  condition  and,  with  new  indicating  parts, 
mount  them  upon  a  stand  so  that  the  lever  can  be  manipulated  the 
same  as  in  the  machine.  Test  the  lever  by  manipulation  and 
actuate  the  indication  or  safety  magnet  after  the  lever  has  come  to 
a  stop.  These  magnets  should  not  operate  on  less  than  the 
minimum  allowable  current.  Any  coil  not  up  to  standard  require- 
ments should  be  renewed.  Not  only  is  the  safe  condition  of  the 
indicating  parts  necessary,  but  all  parts  must  move  freely  while 
the  lever  is  operated.  Where  a  considerable  number  of  inter- 
lockings of  one  type  are  to  be  tested  on  one  road  the  most  efficient 
method  is  to  commence  at  one  plant  and  place  new  indication 
dogs,  latches  and  other  such  parts,  whether  worn  or  not,  in  one 
machine;  then  make  a  careful  inspection  of  the  ones  removed, 
using  only  those  in  good  condition  at  the  next  plant. 

General  Maintenance.  Contact  springs  and  commutator 
springs  must  be  kept  clean  at  all  times. 

Bells  and  buzzers  employed  as  annunciators  in  towers  are  gen- 
erally sheltered  from  the  weather.  The  only  thing  liable  to  in- 
terfere with  their  proper  operation  is  dust  and  dirt  between  the 
contact   points.      Naturally,   a   burnt   out  coil   or   broken   spring 

217 


ELECTRIC   LOCKING 

appears  occasionally.  On  single  stroke  bells  note  that  the  arma- 
ture stops  hold  the  hammer  clear  of  the  gong  when  the  armature 
is  attracted  so  as  not  to  deaden  the  sound. 

Bridge  circuit  controller  contacts  in  particular  should  receive 
frequent  attention  on  account  of  their  exposure.  They  must  be 
cleaned  every  day  in  winter  because  they  quickly  become  frosted, 
owing  to  improper  covering.  On  damp  days  the  plungers  become 
coated  with  moisture,  necessitating  frequent  wiping,  so  as  to 
prevent  high  contact  resistance,  which  will  make  track  circuit 
operation  difficult.  Wire  leads  and  terminal  parts  should  be 
watched  closely  on  bridge  circuit  controllers  as  they  often  break 
and  jar  loose  on  account  of  the  excessive  vibration  to  which  draw- 
bridges are  subjected.  Wires  are  also  susceptible  to  ground  at 
such  places,  caused  by  the  insulation  rubbing  against  the  iron 
work.  Outlying  switch  locks  are  subjected  to  much  rough 
handling  by  train  crews,  who  may  become  impatient  while  waiting 
for  a  switch  release.    They  should  receive  frequent  inspection. 

Renew  the  oil  in  the  cylinder  on  liquid  time  releases  twice  a 
year  by  refilling  with  thin,  non-freezing  oil. 

Contacts  exposed  to  the  weather,  such  as  switch  box  contacts 
or  contacts  on  the  signals,  must  be  inspected  more  frequently  than 
other  contacts.  The  gaskets  on  the  covers  of  such  circuit  con- 
trollers should  be  in  good  condition  so  as  to  have  the  contacts 
protected  from  the  weather. 

Failures.  Improper  manipulation  of  emergency  and  screw 
releases  by  the  leverman  results  in  many  failures  and  causes  the 
maintainer  a  great  deal  of  trouble.  With  screw  releases,  for  ex- 
ample, they  effect  the  release  by  reversing  it,  but  fail  to  place  it 
normal  again,  perhaps  because  at  that  particular  moment  the  sig- 
nal which  breaks  through  the  normal  contact  is  not  to  be  cleared ; 
or  perhaps  because,  while  the  leverman  worked  the  release,  he 
was  interrupted  by  the  dispatcher  and  forgot  about  the  release  un- 
til a  train  startd  to  whistle  for  a  signal.  Hence,  in  many  cases  the 
release  may  be  left  half  way  over,  which  will  prevent  the  clearing 
of  the  signal  and  necessitate  calling  out  the  maintainer  to  locate 
the  suspected  trouble.  For  this  reason,  where  electric  locking  is 
employed,  many  maintainers  make  it  a  practice  to  look  at  the 
screw  releases  first  when  they  are  called  out  for  a  failure.  Con- 
tacts on  cut-out  keys  for  annunciators  have  also  caused  delays  on 

218 


MAINTENANCE 

account  of  being  bent  or  in  a  shape  which  prevented  their  making 
good  contact.  It  is,  therefore,  important  that  they  be  inspected 
and  cleaned  frequently  in  order  to  insure  the  proper  contact  being 
made  at  all  times. 

In  cases  of  failures  always  ascertain  first  whether  it  is  a  circuit 
failure  or  a  failure  of  the  apparatus ;  if  a  circuit  failure, 
proceed  to  discover  which  circuit  is  affected.  In  many  cases  one 
failure  may  lead  to  another ;  but  in  all  cases  locate  the  basic  cause 
of  the  failure  and  remedy  it  before  attempting  to  locate  other 
derangements  of  the  deranged  circuits.  As  an  example  of  how 
to  proceed,  a  stick  relay  circuit  failure  will  be  taken  for  illustra- 
tion. Failures  on  such  circuits  may  happen  by  the  stick  relay 
failing  to  drop  or  pick  up  when  it  should.  When  testing  for  fail- 
ures on  a  normally  open  stick  relay  circuit  it  is  desirable  to  dis- 
connect the  stick  circuit  at  the  relay  point  and  then  conduct  the 
tests  in  a  regular  manner. 

When  testing  a  normally  closed  stick  relay  circuit  it  is  desirable 
to  close  the  stick  circuit  by  placing  a  temporary  jumper  around 
the  relay  stick  contact  and  then  conduct  the  test.  As  the  stick 
relay  occupies  an  important  place  in  an  electric  locking  circuit 
and  changes  as  above  suggested  may  create  dangerous  conditions, 
it  is  evident  that  even  temporary  alterations  of  this  kind  should 
be  made  only  after  all  precautions  have  been  taken  to  guard 
against  any  circumvention  of  the  electric  locking  protection.  It 
may  often  be  desirable  to  have  a  man  located  at  the  relay  to  make 
the  alterations  only  when  the  electric  locking  is  not  effective. 

After  a  circuit  has  been  disconnected,  wires  replaced,  or  the 
cause  of  the  failure  of  a  circuit  remedied,  its  operation  should  be 
tested  before  again  being  placed  in  regular  service.  This  can  be 
done  during  the  next  train  movement  over  the  plant,  but  if  none 
is  likely  to  occur  within  a  reasonable  length  of  time,  create  a 
condition  which  will  make  a  similar  check  possible.  In  all  cases 
the  test  must  be  made  as  near  a  duplicate  of  the  regular  operation 
of  the  circuit  as  circumstances  permit. 

THE    END 


219 


UNIVERSITY  OF 


111 

!f  Si  90842051 9j 


